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The purpose of this thread is to help focus the attention of the community on posts that may require reopen and undeletion votes. A request should be posted as an answer below (one request per answer).

Some guidelines:

  • Please be polite, and respect the many different viewpoints in our diverse community. This goes for the person making the request as well as those commenting on it.

  • There is a reopen queue. Please wait until a post has gone through this queue, before posting here. Notice that the first edit after the question was put on-hold pushes the question into reopen review queue, if the edit was done within 5 days of closure. So does a reopen vote. (If the review has already been finished, it is shown on the timeline of the question.) In doubt, wait 24 hours after the last substantive action.

  • To inform readers of the current (and past) states of the targeted post, please add once the request resulted in some action the information Reopened or Undeleted at the start. (If it the action is undone, add this too, like Reopened, reclosed.)

  • Do not only post a request, like "request reopening of ". Instead make a case for your concern. Yet keep in mind that it can be easier to get your request handled if you try to frame in a away that takes the feedback the post received into account in a positive way rather then seeking confrontation. Also, try to improve the post before posting here.

  • In case of "small" requests, like one missing vote, it can make sense to ask in chat instead of posting here. The room CRUDE is a reasonable place for such requests. The same guidelines apply there.


Earlier versions of this thread that served as a model:

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54 Answers 54

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Reopened


This is on the chopping block again: Is zero a prime number? The question was the subject of this meta discussion: How to prevent the loss of excellent answers to poor questions. which resulted in reopening.

(Disclosure, I have a solution on the question. I feel the question and solutions are worth fighting for, in this case.)

The reason this time for closure is "too broad", but it is far from obvious that this objection is valid. The OP asks three complete and answerable questions, two of which have answers elsewhere on the site. The remaining question became the focus of some of the answers, and there does not appear to duplicate with comparable content.

So for all intents and purposes, there is a single, clear question that seems rather likely for a layperson to ask, and there are good answers. There is nothing about the breadth of the question which inhibits solutions, as can be seen.

Furthermore, on the holistic side, after so many upvotes on the question and its solutions, and approaching now 30000 views, it seems that the post IS manifestly useful. So, I request your votes to re-open this.

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    $\begingroup$ I agree that this rather should not be closed, especially after the improvement of the post. (Yes, the question still has some shortcomings, but I feel it is "good enough".) I tangentially got involved last time; but stopped short of taking action. I reopened it now. (This is less of a so-called unilateral action as it was 'nearly' reopened two weeks ago. ) $\endgroup$ – quid Jul 16 '18 at 17:42
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    $\begingroup$ @quid Thank you for your attention to this! $\endgroup$ – rschwieb Jul 16 '18 at 18:28
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    $\begingroup$ @quid I'm curious: my understanding was that closed questions were still viewable and not eligible for automatic deletion (assuming that the question is upvoted and has upvoted answers). Why is it inappropriate to close the question and leave a message to the effect of "This question has been preserved because of a good answer. It is never-the-less not a high quality question." For example, the lock message on this question. $\endgroup$ – Xander Henderson Jul 16 '18 at 19:04
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    $\begingroup$ @XanderHenderson 'Why is it inappropriate to close the question and leave a message to the effect of "This question has been preserved because of a good answer. It is never-the-less not a high quality question.' Why do you use the indicative here? No one did that, as far as I know. In any case not recently. The question was reopened after a substantive edit, and then reclosed without comment, as 'too broad'. It also had a delete vote. Maybe more to the point, I would not consider it as inappropriate. But frankly given the edit I don't consider the question as all that bad. $\endgroup$ – quid Jul 16 '18 at 20:57
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    $\begingroup$ Sure, it is a bit of a laundry list, and the last question is a bit strange, but in it's naive way even this seems like a genuine question. But it is also not unreasonably broad. Would it be asked now, I'd recommend to split it up, maybe. But this is not easy to fix now, and maybe not that important either. Maybe the combination of question even can be seen as hinting at the level at which the questions is asked. To only ask "is zero a number" might be ill-posed or underdefined, but in context I think it works. $\endgroup$ – quid Jul 16 '18 at 21:04
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    $\begingroup$ Then there is also a community-aspect. Somebody actually put some non-trivial effort into improving this question, and the result is not that bad. If even this is not enough, at some point the line of argument that users should improve post they care about loses credibility, which leads to less improvements. @XanderHenderson $\endgroup$ – quid Jul 16 '18 at 21:10
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    $\begingroup$ @quid I apologize---my original comment was poorly phrased, and likely not really related to this reopen request. A better phrasing might have been "In cases where there are really good answers to questions of marginal merit, (1) don't those answers automatically get preserved even if the question is closed? and (2) can such answers be protected? Since you seemed kind of ambivalent with respect to reopening (which I see now was an over-interpretation on my part), I was asking about an alternative. $\endgroup$ – Xander Henderson Jul 16 '18 at 23:38
  • $\begingroup$ In any event, thank you for the feedback. I honestly do value it. :) $\endgroup$ – Xander Henderson Jul 16 '18 at 23:39
5
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Reopened


The question A Proof of the Fundamental Theorem of Arithmetic was rightfully quickly closed as unclear, but the asker has since edited to clarify what they meant and what specific difficulty they had adapting the standard proofs to get what they want. It seems to me to be a perfectly reasonable question which is mostly clear (though a constraint like "not using integers or rational numbers" is inevitably going to be a little slippery).

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5
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Reopened

I edited the question Variable in upper bound of sum when it had 4 votes to close, and I also posted a rather detailed answer (which the OP accepted). It got "put on hold as unclear what you're asking" even though I think it's now quite clear and on-topic. Can the question be re-opened?

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5
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Reopened, Put on hold, deleted, undeleted, deleted, re-undeleted, re-deleted, undeleted again, deleted again, locked, unlocked and reopened

Please consider reopening What digits is the "number" $\infty$ composed of?. This question was closed as "not about mathematics". Obviously, this question is based on some misconceptions of what infinity is, but they are perfectly natural misconceptions for a layman and that hardly makes the question "not about mathematics". The question has a nice answer which clarifies the misconceptions and is a valuable addition to the site.

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    $\begingroup$ I agree. Voted to reopen. $\endgroup$ – Brahadeesh Nov 13 '18 at 8:28
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    $\begingroup$ I don't think having that question around helps us in building a useful math Wiki, which is what the founder of the site had in mind. $\endgroup$ – Jyrki Lahtonen Nov 22 '18 at 10:26
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    $\begingroup$ Questions like this have really interesting and revealing answers. I'm thinking about padic numbers and infinitely long strings of digits depending on the base, but I feel like I'm denied my reopen vote by the vigilantes who co-ordinate their fast deletion vote, so minimally many users have the power to reinstate it. $\endgroup$ – user334732 Dec 1 '18 at 21:39
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    $\begingroup$ I don't think the question is particularly bad, and not worth deleting. It addresses some common, layman misconceptions, and I don't think that is such a bad thing. (Maths suffers from a poor understanding at all levels of society - let us do what we can to help!) Also, the question is 4 years old. I favour keeping open older questions rather than judging them by todays standards. $\endgroup$ – user1729 Jan 30 at 19:58
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    $\begingroup$ The question is currently undeleted but closed. The questioner seems aware that "infinity" might not actually be a number in the usual sense, but so far there's no answer explicitly saying how it differs from numbers. I would like it reopened to allow someone to post one. $\endgroup$ – timtfj Feb 5 at 12:32
  • $\begingroup$ @timtfj: It is deleted again. Some discussion regarding the recent deletion can be found in the CRUDE chatroom. $\endgroup$ – user 170039 Feb 5 at 15:32
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    $\begingroup$ @JyrkiLahtonen I disagree that the question is without use. I think a plausible-yet-naïve-question like this one has a lot of utility to resolve a misconception that others are probably going to have. I can't say I like this particular question, but I can say that I think it's dumb in this case to work so hard to delete it. (It seems to me that a useful wiki would want mechanisms to resolve misconceptions, anyway. Full disclosure: I don't really buy into math.se-as-a-wiki.) $\endgroup$ – rschwieb Feb 6 at 14:57
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Closed, re-opened

Solve for $x^2 + 7x +1 = 3n(x^2 + x +1), n \in \Bbb{Z}$ My this question was put on hold as off-topic because it lacks context. It also gives a link to how I can add context. The link gave the following points

  1. Include your work My response - I answered that question which I asked. I got a few hints from the comments which helped me. Should I give a summary of my solution it the question?
  2. Motivation for question-
    My response - I said in the details of the question that the original problem was a trigonometric equation which I solved but was stuck there.
  3. Where did the problem come from? My response- it came from a book which is suppose to help me in my College entrance exam. But in this context it is really irrelevant and rather obvious.
  4. give your background My response- I did give my background. I am a high school student who is self studying for college entrance exam.
  5. reference My response- None exist.

I am not critising the one(many) who put my question on hold because nobody have to answer my question as this site is run by volunteers. I am just curious. How can I improve my question?

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5
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Closed, re-opened

Please consider reopening What is wrong with this solution of find the least value of $ \sec^6 x +\csc^6 x + \sec^6 x\csc^6 x$.

  • This question is closed as a duplicate of this previous question by the same OP: Find the least value of $ \sec^6 x +\csc^6 x + \sec^6 x\csc^6 x$ but the two questions are different. The closed question asks why a particular method of solution does not work, which is very different from the duplicate target.

  • Perhaps relevant: the OP has also posted this question on Meta asking about the site policies on marking posts as duplicates (in general, and not pertaining to the reopening of this specific post).

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  • $\begingroup$ Also, OP has indicated that he/she no longer cares about the question, and in particular is not seeking reopening. $\endgroup$ – Gerry Myerson Apr 19 at 22:34
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    $\begingroup$ @GerryMyerson True, but the post itself belongs to the community and I feel it is worth reopening, hence the request. $\endgroup$ – Brahadeesh Apr 20 at 0:53
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Undeleted

As per quid's advice, I would like to request that Number of real roots of an iterated quadratic: $x^2-3/2$ be undeleted. The question was self-deleted within a few minutes of my posting an answer which claimed that the conjecture of the question was false, so the reason for the deletion appears to be embarrassment. However, the question itself was an interesting one, as evidenced by more than 10 upvotes and 7 stars.

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4
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Reopened

I request a reopen of Are the corner hypercubera polytopes self-dual?. The question provides a v-definition of an infinite family of polytopes, and asks whether each member of this family is self-dual. (I don't see anything unclear about this question.) Other than being closed for being unclear, I haven't received feedback on this question.

I believe this Q&A provides the first known example of an infinite family of self-dual polytopes that is not a set of k-fold pyramids over a self-dual polytope.

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    $\begingroup$ The post reads as a blog post, not a question. It needs to be vastly more concise, and I frankly don't think that MSE is a good site to ask questions like this; you would do better just talking to someone in the field. You got a bit of feedback in your last meta post. $\endgroup$ – T. Bongers Oct 1 '18 at 23:20
  • $\begingroup$ Thanks for replying. I agree that a tag pertaining to just a question or two need not exist. As to the question, 1/3 of it is motivation, which I understand to be a requirement of MSE (I would just as soon leave it out). The answer is long because, while conceptually simple, the proof has a lot of tedious parts to it. $\endgroup$ – Dan Moore Oct 2 '18 at 0:35
  • $\begingroup$ I've made my question more concise-it's now about 1160 characters & fits on my small Mac screen. My answer is about 18,000 characters. To analyze why it's so long, I counted the characters in eight distinct parts of the answer. Some parts are long because the thing to be proved requires a lot of words (wishing there was an elegant proof doesn't make it so). $\endgroup$ – Dan Moore Oct 2 '18 at 23:56
  • $\begingroup$ Strictly speaking, the question was closed, not the answer. The Q&A is good because it sets forth the first example (ever in the history of mankind) of an infinite family of self-dual geometric polytopes (one for each dimension d $\ge$ 3) which aren't a set of k-fold pyramids over a self-dual polytope. $\endgroup$ – Dan Moore Oct 3 '18 at 0:00
  • $\begingroup$ I've improved my answer by adding headings, allowing the reader to more easily navigate or skim the answer. $\endgroup$ – Dan Moore Oct 7 '18 at 15:47
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Reopened

I would like to see the question "What is $\nabla X$ in Riemannian geometry?" re-opened. (I see from the timeline that the reopen queue has finished. In hindsight, I should have edited the title when I made the reopen vote.)

It appears it was marked as a duplicate of Gradient of a vector field?, seemingly because the short version of the question (and the old title, "What is $\nabla X$?") is very similar. But I would say that the rest of the question and the context (including tags) make it a question that necessitates an answer that would be inappropriate on the other question. "Gradient of a vector field?" has a tag and context of multivariable calculus, not Riemannian geometry.

Since "What is $\nabla X$ in Riemannian geometry?" doesn't yet have an accepted answer, I would like it re-opened so others can contribute.

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Reopened

The OP added an attempt to Determine the number of ordered triple $(x, y, z)$ of integer numbers (negatives and positives) satisfying $|x| + |y| + |z| \le 6$ in a comment to an answer while there was still only one close vote. I have moved that attempt to the question. I think that the question now meets the criteria for context.

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  • $\begingroup$ Doesn't the question now contain a complete solution to the problem? which makes it a pretty peculiar question? $\endgroup$ – Gerry Myerson Mar 28 at 21:53
  • $\begingroup$ It gives context, which was why the question was closed. It doesn't really matter to me since I've already answered the question. Questions are not closed when the OP answers them, so I thought this one shouln't be closed for lack of context. Other answers might provide different insights. $\endgroup$ – robjohn Mar 28 at 23:29
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Reopened

This question I asked was closed for lacking context. After context was added, the hold was never lifted, and eventually was closed.

$X,Y$ not homeomorphic if $X\backslash x$ is disconnected for all $x\in X$ but $Y\backslash y$ is connected for some $y\in Y$

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Reopened, then closed as off topic, deleted

This question (does the existence of an lcm in a commutative ring imply the existence of the gcd of the two elements) was closed as a duplicate, pointing to this one (which shows inter alia that the existence of an lcm in a domain implies the existence of a gcd). In fact, I had done the same thing yesterday.

However, this is not a real duplicate. The question here is about rings, whereas the alleged duplicate is about domains. The proof there does not easily translate: for example, the first step of the proof in the question pointed to is to take $m=\mathrm{lcm}(a,b)$, let $s$ be such that $ms=ab$, write $m=ar$ and $m=bt$, and then claim that $s=\gcd(a,b)$. The first step is to show $s$ divides $a$, which it does by showing that $(ab/m)*(m/b)=a$. This is equivalent to saying that $st=a$; but I do not see how to conclude this in a ring (in a domain, multiplying through by $b$ and then cancelling will do it, but how do you do it here?).

As I had already closed it, and then re-opened, I can no longer vote to re-open on the page.

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    $\begingroup$ Were it me, I would have voted to close the question for lack of context. There is zero context. Where did the question come from? What is the background of the asker? Why should anyone care about that question. It really isn't a very good question, and it probably should be closed. $\endgroup$ – Xander Henderson Sep 4 '18 at 3:48
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    $\begingroup$ @XanderHenderson: That's valid, but the problem right now is that it points to a question claiming that it provides an answer when it does not. $\endgroup$ – Arturo Magidin Sep 4 '18 at 3:53
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Reopened, closed, reopened


I just came across this question: Derivative of Square Root Visual after failing a reopen review audit and I'm wondering why it's still closed: unclear what you're asking. I agree that the MathJax formatting isn't the best, but it is still readable.

The OP has actually shown what they've tried, and what they didn't get, so the reason for closure is beyond my understanding. I thus request to reopen the question.


I have now edited the question to make it look neater.

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  • $\begingroup$ Well it is definitely unclear what they are asking... One has to take roughly 10 mins to watch the youtube videos to see what they are trying to say (watching parts of 2:25 and 12:48 don't quite work, at least to me). $\endgroup$ – user99914 Jul 17 '18 at 10:32
  • $\begingroup$ @JohnMa I think they meant 3:25, as it looks much more relevant? $\endgroup$ – TheSimpliFire Jul 17 '18 at 10:43
  • $\begingroup$ They start the $x^2$ example at 2:35, and then to power rule (up to 10:30). Then they switch to $1/x$ (it seems this is the more relevant one). $\endgroup$ – user99914 Jul 17 '18 at 10:50
  • $\begingroup$ This question is now reclosed as "off-topic". $\endgroup$ – Brahadeesh Apr 12 at 23:12
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    $\begingroup$ Thanks for the update @Brahadeesh. It's now reopened. $\endgroup$ – TheSimpliFire Apr 13 at 9:33
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Closed, deleted, undeleted, deleted, undeleted, deleted, undeleted, reopened, closed, deleted, undeleted, deleted, undeleted, deleted, undeleted, reopened

This is being deleted repeatedly by the same people even though it has a great answer. There are several votes to reopen. I think it should be reopened because of the answer.

Cevians $AD$, $BE$, $CF$ are concurrent, as are cevians $DP$, $EQ$, $FR$; show that $AP$, $BQ$, $CR$ are concurrent

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    $\begingroup$ By my standards the Question has sufficient context in respect of the OP's remark (in the original body of the Question) that we should try to apply Ceva's Theorem. $\endgroup$ – hardmath Jan 12 at 19:40
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Please consider undoing the duplicate votes here. The duplicate target is quite different as it asks for algorithms while this questions asks for easy ways to calculate determinant (so that careless errors are less likely to commit). The duplicate target is a poor question without context (though with some decent answers).

FYI: It failed the reopening review five times before, as of 3rd Sept. 2018.

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    $\begingroup$ Two points: 1. did you ask the user that put it on hold as duplicate about it? 2. It seems that the answer on the dupe target includes the answer on the original question. // Personally I think the answer given on this question is pretty much besides the point. And the question is very localised. Long story short. I'd delete post. $\endgroup$ – quid Sep 3 '18 at 11:59
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    $\begingroup$ @quid: I didn't (I thought this case is obviously wrong, and it had 4 reopen votes already). I agree that the question is localised and deletion is also a good choice. $\endgroup$ – user99914 Sep 3 '18 at 15:21
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Reopened

Please, consider reopening this question.

The question was somewhat unclear when first asked, but was pinpointed down in comments. I also edited it providing a figure which helps to readily understand the situation.

The context provided by OP (by means of the "planified" picture) makes the source of confusion clear, and now that the problem itself is also clear, I think it fits the site well.

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Undeleted.

I nominate Is the numerical range of Identity operator convex? for undeletion because the question asker self-deleted her question shortly after receiving an answer from a high-rep user. That's an abuse of the system.

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Reopened.

This recent Question asks about a variant of the Secretary Problem which as far as I can tell has not been previously answered here.

I mistakenly proposed to close as a duplicate of the classic Secretary Problem, but this variant treats as equally successful the choice of either the best or the second-best candidate. Please consider adding your vote to reopen to mine.

[NB: I edited the title of the post to clarify that this is not identical to the earlier Question, and I discuss in the comments there what little Math.SE discussion there had been on this variant (without supplying its literature references).]

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    $\begingroup$ I've edited the question to refine the formatting and grammar a bit, and to use more gender neutral language. I don't think that the question is all that great (it is a problem statement question with a largely nonsensical "attempt"), but I agree that it isn't a duplicate question, and it is somewhat better than much of the stuff that gets posted. In any event, the question is now open again. $\endgroup$ – Xander Henderson Nov 27 '18 at 2:27
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Undeleted, closed, deleted, re-undeleted, reopened

I nominate How to use derivatives to prove that $f(x)=2\cos^2\left(\frac{\pi }{4}-\frac{x}{2}\right)-\sin \left(x\right)=1$? for undeletion since OP has self-deleted his/her question after receiving an answer. This is unacceptable on Math.SE.

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  • $\begingroup$ It's better to write self-contained posts. In the current case for the moment there was no big risk, but it's still not ideal. $\endgroup$ – quid Nov 8 '18 at 19:42
  • $\begingroup$ @quid Thanks for your intervention. I'll correct this now. $\endgroup$ – GNUSupporter 8964民主女神 地下教會 Nov 8 '18 at 19:44
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    $\begingroup$ I don't understand why this question was closed and deleted by users. It is not unclear what they're asking. (It may not be true, but it is certainly clear!) $\endgroup$ – user1729 Feb 5 at 11:28
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    $\begingroup$ @user1729 Some users don't like wrong info in the question. They have standards so high that $D(\sin x)$ and the RHS of $f'(x)$ doesn't please them. It's possible that they used their power to get rid of this question. $\endgroup$ – GNUSupporter 8964民主女神 地下教會 Feb 5 at 11:37
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    $\begingroup$ It's definitely not unclear—the questioner gives the problem, shows what they did, and asks what's wrong with it. I think it could do with an additional answer which makes crystal clear what the error was and how the (interesting!) technique works, and reopening would allow someone to post that. $\endgroup$ – timtfj Feb 5 at 12:06
  • $\begingroup$ @timtfj It's now reopened. $\endgroup$ – GNUSupporter 8964民主女神 地下教會 Feb 5 at 16:04
  • $\begingroup$ @GNUSupporter8964民主女神地下教會 At least it's clear that their expectations could never rise to match the size of your assumptions... $\endgroup$ – Lord_Farin Feb 6 at 17:34
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Undeleted, then deleted again, then undeleted again, then reopened, then closed again, then reopened again

Please undelete Compare $\arcsin (1)$ and $\tan (1)$ because OP has made an observation $\sin(\tan1)\leq1$ in order to compare the two quantities in the question title. This question has

  • 4 net upvotes;
  • 3 $\star$;
  • 2 (ex)-moderators' answers; and
  • 1 Undelete vote remaining to save this question.
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Reopened

Please reopen this this question. One user @lulu stated the question was clear but it is still closed.

If the question is unclear, state why?

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2
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Undeleted, then closed and deleted

I think there's a consensus that we undelete questions when they are deleted by the user who posted them after someone else has posted an answer (see, for example, the comment here: https://math.stackexchange.com/questions/2759560/extending-the-triangle-inequality#comment5694741_2759560). In accordance with that consensus, I propose undeletion of https://math.stackexchange.com/questions/2840649/solutions-to-sum-j-ok-r-j23r-j2-equiv-0-mod-p

Now I'll own up that I'm the one who posted the answer to the question. My answer was exceedingly terse, and came out of a review with the note, "This does not provide an answer to the question (and so on, and so forth)." But it does provide an answer. The question was to prove or disprove that there are no solutions to a certain equation (congruence, actually, but never mind), and my answer gave a solution.

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    $\begingroup$ Is this actually a consensus? $\endgroup$ – Did Jul 23 '18 at 12:30
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    $\begingroup$ @Did, if you look at the previous edition of this thread, you'll find that in April-May, GNU Supporter posted 4 requests for undeletion, all on the grounds that OP had deleted a question after receiving an answer, and all four questions were undeleted. $\endgroup$ – Gerry Myerson Jul 23 '18 at 12:51
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    $\begingroup$ Yes, and? $ $ $ $ $\endgroup$ – Did Jul 23 '18 at 18:11
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    $\begingroup$ @Did For what it's worth, I have the same impression about the consensus. Preventing an asker from covering up their own question seems to be something the community values, even if it's closed later. $\endgroup$ – T. Bongers Jul 23 '18 at 18:35
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    $\begingroup$ @T.Bongers (and also Gerry Myerson): I think that there is a moderate consensus that it is bad form to ask a question, get an answer, then delete the question. It belies an ignorance of the functioning of the site (i.e. questions are supposed to be helpful to everyone, not just the one person asking the question). However, in this particular case, the question is of pretty low quality, and should be closed and deleted (in my opinion). It seems like a waste of resources to have opened it back up again... $\endgroup$ – Xander Henderson Jul 23 '18 at 19:00
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    $\begingroup$ For what it's worth, I have expanded my answer to the question on main. $\endgroup$ – Gerry Myerson Jul 24 '18 at 0:34
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    $\begingroup$ "For what it's worth, I have expanded my answer to the question on main." On this topic, my understanding is that the consensus is that a good (or even great) answer is not really enough to justify keeping a poor question around. This and this are relevant. $\endgroup$ – Xander Henderson Jul 24 '18 at 13:27
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    $\begingroup$ @Xander, the highest-voted answers and comments on your first link hardly support your understanding. The second link, even there there is considerable support for not deleting questions with good answers. I'm not convinced there is, was, or ever will be a consensus on this issue. A majority, maybe, but no consensus. $\endgroup$ – Gerry Myerson Jul 24 '18 at 21:31
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    $\begingroup$ @GerryMyerson I think you and I must be reading very different answers. In answer to the question of whether bad questions with good answers should be preserved, my reading of the top three answers ((1), (2), (3)) suggest that it might be worth protecting a poor question if it hosts an excellent answer. $\endgroup$ – Xander Henderson Jul 24 '18 at 22:54
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    $\begingroup$ On the question of upvoting poor questions with good answers, the top voted answer is this one, essentially "I don't do it, but there could be an argument in favor of it." The second answer is similar, with the idea being that a good answer should be preserved if it might be helpful for others in the future. $\endgroup$ – Xander Henderson Jul 24 '18 at 22:55
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    $\begingroup$ In both cases, it seems clear to me that the consensus is that it might be reasonable to preserve a poor question if it attracted a really good, useful, generally helpful answer. Again, a good answer (or possibly even a great answer) is not, by itself, enough to preserve a poor question. $\endgroup$ – Xander Henderson Jul 24 '18 at 22:58
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    $\begingroup$ Finally, I note that I made my initial comment in response to your assertion that you have improved your answer. Are you further asserting that the improvements created something that is of such lasting value that it will be beneficial beyond asking that poor question? Despite the fact that this question and answer have been the topic of discussion here for a couple of days, your answer has not attracted any upvotes... $\endgroup$ – Xander Henderson Jul 24 '18 at 22:59
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    $\begingroup$ @Xander, I'm not in it for the upvotes. I objected to a user posting a question and then deleting it when it got an answer, as I agree with a moderator that such an action is an abuse of the site. Once the question was undeleted, I took the opportunity to improve my answer, in response to a comment from another user. What's wrong with that? I'm not asserting anything about the lasting value of the question or the answer, other than the answer being fuller now than it was. The answer may help someone coming along who is interested in sums of two squares modulo a prime. Fire away. $\endgroup$ – Gerry Myerson Jul 24 '18 at 23:30
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    $\begingroup$ @GerryMyerson: it isn't pleasant to see one's own answer deleted, but in this case the question is clearly not up to many users' standards, so I think it is not surprising to see it deleted. At this point, the question is no longer deleted by the OP, but by several other users. $\endgroup$ – Carl Mummert Aug 5 '18 at 21:06
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    $\begingroup$ @Carl, it isn't pleasant to see any answer with nonzero mathematical content deleted. More to the point, I would not have put the question up for undeletion, had it been deleted by votes of users. My objection was to OP abusing the site by deleting the question after getting an answer. I thought that was clear. $\endgroup$ – Gerry Myerson Aug 5 '18 at 23:09
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Reopened

Please re-open this question which is put on hold:

Understanding De/Suspension $\Sigma^{-1}(\Sigma{X})\neq X$

It was said that "unclear what you're asking" and people do not know the def of de-suspension.

However, the suspension is introduced earlier in the cited question:

The suspension (topology) and elementary examples

While the desuspension is also quoted/linked to the Wikipedia (withe refs given by Wiki). I also include a new note: "The desuspension is arguably firstly introduced in the cited text mentioned in H. R. Margolis (1983). Spectra and the Steenrod Algebra. North-Holland. p. 454." And the ref cited.

Follow people's comments, I modify to also ask the basic definitions:

Question: How do we define desuspension exactly? (Please see the comments below, people complain about the meanings of desuspension in Wikipedia is useless).

Are we able to have the desuspension acting on the topological space as the suspension does? Or do we only have the desuspension act on the spectra but not the space?

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Reopened

Please consider reopening this. It was closed originally as missing context. The OP provided some context in the comment and I have added a little bit more. Hope it is okay now.

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  • $\begingroup$ Wow, this question was through reopen review queue already four times. It makes me wonder what is the record. $\endgroup$ – Martin Sleziak Sep 1 '18 at 1:04
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    $\begingroup$ I think it just how difficult it is to reopen a post using only the review queue. @MartinSleziak $\endgroup$ – user99914 Sep 1 '18 at 13:00
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    $\begingroup$ This one has 5 and is still closed. $\endgroup$ – user99914 Sep 1 '18 at 13:01
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Reopened

Please consider reopening the question A functional equation of a matrix that is placed On Hold. I have added my attempt at the cracking the problem if the lack of it was the reason for placing it on hold. The question itself is technically perfectly sound.

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    $\begingroup$ You should have just edited your previous answer, and not added another "answer." $\endgroup$ – Joel Reyes Noche Sep 25 '18 at 7:07
  • $\begingroup$ @JoelReyesNoche: What do you mean? "Answer" to my question that I linked to? I did not post an answer to my own question. $\endgroup$ – Hans Sep 25 '18 at 8:18
  • $\begingroup$ No, answer(s) on the present meta page, there should not be two for a single post on main. $\endgroup$ – Did Sep 25 '18 at 9:31
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    $\begingroup$ I have removed the second post, since this one has been edited to indicate the reopening. I've also edited and deleted/undeleted, so whomever downvoted can undo their vote. $\endgroup$ – Asaf Karagila Sep 25 '18 at 9:56
  • $\begingroup$ @AsafKaragila: Oh, sorry. I did not know the first request was posted as I remembered closing the page rather than posting the "answer" as I needed to leave in a hurry earlier. I posted the second request thinking that the first request was not posted. This is the first time I post in the meta question site. $\endgroup$ – Hans Sep 25 '18 at 10:59
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    $\begingroup$ Why this post says "reopened" when the linked question is still on hold at the moment? $\endgroup$ – Martin Sleziak Sep 25 '18 at 12:31
  • $\begingroup$ @Martin, seems to have been a mistake, which I have rectified. $\endgroup$ – Gerry Myerson Sep 25 '18 at 12:37
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    $\begingroup$ The thing that is missing in the current version of the question, more than work, is the source of the problem. Why do we expect it is true in the first place? $\endgroup$ – Carl Mummert Sep 25 '18 at 19:32
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Undeleted, redeleted, undeleted again, reopened

Statements that look obviously false but cannot be disproved. is at $+15$, and has answers at $+7,+10,+14,+20,+21,+8$, and $+15$. Please consider voting to undelete. [In the interests of transparency, I note that the $+15$ answer is mine.]

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    $\begingroup$ I agree that the question is highly upvoted and has highly upvoted answers. That does not make it an appropriate question for MSE. With regard to what is on-topic, it isn't a problem or puzzle, and I see no clear indication that there is a particular topic that needs to be clarified. With respect to what not to ask, the question seems designed to engender discussion, not to seek explanation. $\endgroup$ – Xander Henderson Sep 27 '18 at 16:35
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    $\begingroup$ For the benefit of the people who cannot see deleted questions, I'll add that this MO question is mentioned in comments: The most outrageous (or ridiculous) conjectures in mathematics. (Even if this one does not get undeleted, the linked MO post might be interesting for people who would consider Statements that look obviously false but cannot be disproved interesting.) $\endgroup$ – Martin Sleziak Sep 28 '18 at 8:42
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    $\begingroup$ @XanderHenderson Just curious, what would you then consider as on-topic for the soft-question and big-list tags? $\endgroup$ – dxiv Oct 4 '18 at 5:51
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    $\begingroup$ Surely we have better things to do that relitigate this post over and over again, and remove the collective efforts of 16 people. I see no harm from the existence of this post, except for the ruffled feathers of people who are inclined to overmoderation. $\endgroup$ – T. Bongers Oct 4 '18 at 22:13
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    $\begingroup$ In my opinion, if some want content and others do not then it should stay. The veto should be over removal rather than the converse. I will never understand why it's so important to wreck somebody else's party. $\endgroup$ – user334732 Dec 1 '18 at 18:22
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Undeleted

The deleted answer for Show that there does not exist a unique stationary distribution. should be undeleted.

The question is about "existence of unique stationary measure", and the answer is concise and to-the-point.

"$(1,0,0,...,0)$ and $(0,0,...0,1)$ are two invariant distributions so uniqueness fails."

The existing answer shares the same idea with the deleted one, and it has passed a Low Quality Review.

(Edit: comment removed)

The deleted answer attracted an comment from a high-rep user during another Low Quality Review. However, by appealing to his/her tag score for the relevant tags (, , , , , etc) (and the contributing posts) and comparing them with those of the answerer, you'll have a better idea about their contributions to the site in those areas.

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    $\begingroup$ Oddly, the deleted answer was deleted, not through review, but by its owner. $\endgroup$ – Gerry Myerson Oct 12 '18 at 11:51
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    $\begingroup$ You could ping the author on another of his posts, but I generally oppose undeleting a self-deleted post. $\endgroup$ – T. Bongers Oct 12 '18 at 15:14
  • $\begingroup$ The author has commented on the other answer, so he can be pinged there if necessary. This is an odd situation. $\endgroup$ – Arnaud D. Oct 12 '18 at 17:34
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    $\begingroup$ Thanks for advice. I did ping the author. He can undelete this anytime he wishes. I ponder whether CRUDE is healthy, when some of its active users vote to delete short answers outside their familiar tags regardless of the quality of the answer. This isolated example shows that its malfunctioning in terms of quality control. $\endgroup$ – GNUSupporter 8964民主女神 地下教會 Oct 12 '18 at 20:35
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    $\begingroup$ @GNUSupporter8964民主女神地下教會 This isolated example shows nothing about CRUDE, since the delete votes and the associated comment came from the review queue, and the answer was never mentioned in CRUDE. Besides, I'm not sure tag scores are necessarily an indicator of expertise : for example I have a low score in "integration" because I don't really like to compute integrals, but I still know the basics and I think I'm competent to judge the quality of reasonably simple answers on the topic. $\endgroup$ – Arnaud D. Oct 15 '18 at 12:11
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    $\begingroup$ @ArnaudD. I see your points, but let me clarify my stance. 1. To be more precise, I would say that this post shows the influence of CRUDE participation on other posts (not listed on CRUDE). In a review queue, it's possible that one votes to close/delete within a few seconds. Given the amount of posts that they review every day (in/outside CRUDE), this example reminds us the adverse effect of their rare mistakes dispite their high reputation. 2. That's why I've added "contributing posts" inside the brackets. $\endgroup$ – GNUSupporter 8964民主女神 地下教會 Oct 15 '18 at 12:47
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    $\begingroup$ If you read the posts instead of the scores, you'll find out the truth: a) there's no probability theory in his/her "probability theory" answers. These are mistagged (elementary) probability questions. b) His/her stochastic calculus tag score comes from a reference request question. By the way, he/she has removed his/her comment. $\endgroup$ – GNUSupporter 8964民主女神 地下教會 Oct 15 '18 at 12:52
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Reopened, then closed as duplicate.

It would be useful if this question can be reopened, so that it can be closed as a duplicate (see comments to post for more details).

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    $\begingroup$ I am not sure there is much benefit in re-opening questions just to re-close them with alternative close reasons. This particular post really should be expanded significantly, if it is to be saved. Re-opening and re-closing will still probably lead to deletion. In particular, because it is a self-answered post, we can expect much higher standards than a post where the OP genuinely has a question. $\endgroup$ – Carl Mummert Oct 28 '18 at 1:07
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Reopened


There have been at least five questions asking how to prove instances of the general proposition $\log_m(m + 1) > \log_n(n + 1)$ for integers $n > m > 1$:

1. How to know if $\log_78 > \log_89$ without using a calculator? (3 May 2012), with an exemplary answer by user22805.

2. Logarithm inequality problem: $\log_2 3 > \log_3 4$ (27 Sep 2016).

3. Compare $\log_34 $ and $\log_45.$ (24 Mar 2017).

4. How to compare logarithms $\log_4 5$ and $\log_5 6$? (25 Sep 2018).

5. Comparing $\log_5 6$ and $\log_6 7$ (9 Oct 2018).

There have been at least three other questions asking to prove inequalities of the form $\log_a{b} > \log_c{d}$ for integers $b > a > 1$ and $d > c > 1$:

6. Which is bigger among (i) $\log_2 3$ and $\log _3 5$ (ii) $\log_2 3$ and $\log _3 11$. (9 Jun 2013).

7. How can I compare $\log_2 3$ and $\log_3 5$ without using a calculator (5 Sep 2017).

8. Comparing $\log_2 3$ to $\log_3 5$ (6 Mar 2018).

There has also been at least one more complex question in the same broad category:

9.Prove $\log_{\frac{1}{4}} \frac{8}{7}> \log_{\frac{1}{5}} \frac{5}{4}$ (20 Sep 2012).

Most recently, the following question was posted, but it was quickly closed as a duplicate (I confess to being one of those who voted to close it):

10. Comparing logarithms with different bases (23 Oct 2018).

The close message for question 10 reads:

This question already has an answer here: How to compare logarithms $\log_4 5$ and $\log_5 6$? 6 answers

But the only method used to answer a previous question (1-9) that can also be applied to the present question (10) is to find positive integers $m, n$ such that $b^n > a^m$ and $d^n < c^m$ (as in Eudoxus's theory of proportion), so that $\log_ab > \tfrac{m}{n} > \log_cd$.

In a comment (which has now been incorporated into the text of the question), the questioner showed that he was aware of this method, and had already used it to answer his own question. He continues:

However, that method doesn't work for every example, and I wonder if there's a easier way to solve this?

Strictly speaking, any logarithm comparison question could be answered in this way. But that is not always very practical, because one one has to search for suitable values of $m$ and $n$, which may be quite large. Some previous answers state or imply the general rule that $\log_a{b} > \log_c{d}$ if $\tfrac{b}{a} > \tfrac{d}{c}$ and $a < b$, but that rule does not apply in this case. It is interesting to ask if some other rule might be applied, eliminating the need for a possibly haphazard search for $m, n$. Failing that, ad hoc solutions to the present problem are also of interest.

Question 10 meets MSE's selection criteria, so it ought to be reopened.

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    $\begingroup$ The question lacks contract in any event. Most importantly: why were the specific constamts in the problems chosen? If the problem is about arbitrary constants, it should be rewritten to say so. If the OP was already aware of a method to solve the problem, that context should also be in the post. Overall the post does.noy seem to demonstrate much effort to write a good post. $\endgroup$ – Carl Mummert Oct 28 '18 at 16:19
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    $\begingroup$ @Carl On that basis, Diophantus would have a hard time posting a question here! Where, in MSE's rules, does it say that every question must be framed in the most general terms possible? What is wrong with asking a question about particular numbers? Especially as no-one has (yet) posted a general answer or a general question covering this particular case. Finally, even if it were granted (purely for the sake of argument) that an experienced user ought to have asked a more elaborate question, shouldn't a new user be cut some slack? $\endgroup$ – Calum Gilhooley Oct 28 '18 at 16:28
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    $\begingroup$ @Carl Also, it was closed as duplicate, and my point is that it is not a duplicate. The close message is a false statement, and the close decision should be reversed. (Of course, anyone can also vote to close it for another reason, and no such person need feel obliged to vote for reopening.) $\endgroup$ – Calum Gilhooley Oct 28 '18 at 16:34
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    $\begingroup$ !Calum: there's no problem posting a question with specific numbers - but it is up to the OP to include adequate context, and the reason for choosing seemingly arbitrary numbers is (in my opinion) part of that context. If this was asked person to person at a department tea, we would expect the asker to say something about the numbers involved. The OP should be encouraged to improve the problem, they have plenty of "slack" to do so. $\endgroup$ – Carl Mummert Oct 28 '18 at 21:19
  • $\begingroup$ I think my guilty conscience over this has now been assuaged. :) $\endgroup$ – Calum Gilhooley Oct 29 '18 at 0:36
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Undeleted


I nominate Group algebra&algebra for undeletion so as to give the community enough time to judge this value of its answer, which is deleted due to the question asker's self-deletion.

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