I recently came across this question which was closed as being a duplicate of that question.

But if we read carefully, we see that there is a slight difference.

In "this question", it's supposed that: $\forall n \in \mathbb N \ , \ x_n<y_n$

In "that question", it's supposed that: $\forall n \in \mathbb N \ , \ \alpha_n < 0 < \beta_n$

And so, the answers to the two questions are different.

In "this question", we may have $\lim_{n\rightarrow \infty} \dfrac{f(y_n)-f(x_n)}{y_n-x_n} \neq f'(0)$ if $f'$ is not continuous.

In "that question", $\lim_{n\rightarrow \infty} \dfrac{f(\beta_n)-f(\alpha_n)}{\beta_n-\alpha_n} = f'(0)$ even if $f'$ is not continuous.

  1. I'm not fluent in english. I would be grateful to anyone who edits this post to correct it.
  2. What should have I done instead of using Meta to expose this problem ?
  • 5
    $\begingroup$ Regarding (2), my first action would have been to comment on the question. This has two advantages: firstly, people interested in the question will see the discussion, and secondly if it enters the "reopen" queue then voters will see the discussion (and so have to think less). If nothing happens for a day or two then there is a dedicated reopen requests thread here. $\endgroup$
    – user1729
    Aug 5, 2021 at 8:15
  • $\begingroup$ (Also, I think you are missing something like "0. Can the question be reopened?" or "0. Am I right and the questions are not duplicates?" - as in you don't actually ask anything about the question. You're question seems fine otherwise and you shouldn't worry about imperfect language/English.) $\endgroup$
    – user1729
    Aug 5, 2021 at 8:19
  • $\begingroup$ I have edited the answer to the second question. The conditions on $\alpha_n, \beta_n$ is used. I have voted to reopened. $\endgroup$ Aug 5, 2021 at 8:58
  • 2
    $\begingroup$ The post is already reopened. $\endgroup$ Aug 5, 2021 at 9:27

1 Answer 1


I am not familiar with limit topic as of yet so I can't tell whether the first is a duplicate of second but I can tell you what to do.

But I can tell you what to do if you arrive at a question closed of duplicate which should not had been closed-

Cast a reopen vote

If you have reputation $\geq 3000$ then besides the edit button there would be a "reopen" button. Just click on that and it will come in Reopen queue and if some number of people also wished to reopen the post the post will be reopened.

In some cases, a single vote is enough to reopen the question:

  • A single vote from a moderator can reopen any question closed for any reason immediately.

  • Questions closed as duplicates can be immediately reopened by a user with a gold tag badge for any of the question's tags.

Try commenting on the post

Just to repeat user1729's comments:

Commenting has two advantages: firstly, people interested in the question will see the discussion, and secondly if it enters the "reopen" queue then voters will see the discussion (and so have to think less)

Edit the post

If the comments are helpful as to why the question has been closed, you can edit the post so that it's a good, on-topic question, or to explain why it's not a duplicate. The close reason, while not always accurate, should point you in the right direction of what to fix. If your edit made others feel it should not had been closed as duplicate it will be reopen

Bring forward the issue in CURED chat room

You can bring forward the issue at chatroom CURED. Just paste the question there and write like

Please unclose this question [link]. This was closed as duplicate but it should not had been closed.

Also if you are not 100% sure whether it should be unclosed just use ask anyone in the room. You can definitely talk to many over there as many of them have enough experience of closing, reopening, deletion or undeletion of question. Some questions are closed/deleted/unclosed/undeleted with help of cured room only but not all. Can't wait to see you there.

Request for reopening of post in reopen post link

If you want to reopen/undelete a post just write a answer over here in the same way others did writing the question and then explaining the reason for reopen and undeletion.

Request on meta to reopen

This one should be used when all three above methods have failed. You can request on meta to reopen a post and tag it with .

To get more help with reopening post you can visit this

  • 5
    $\begingroup$ I think the first two suggestions are in the wrong order. The first and most important thing you should do is comment on the post, giving a reasoned argument (also: "Do, or do not. There is no try."). Starting this conversations lets you work out if you're correct in thinking it is not a duplicate. Once you have worked this out, or some time has passed, then vote to reopen. Voting after this discussion means that everyone in the review queue can see the discussion and so have to think less. $\endgroup$
    – user1729
    Aug 6, 2021 at 9:11
  • 4
    $\begingroup$ (More generally, you say " if you are not 100% sure whether it should be unclosed...". You should never be 100% sure, until you have discussed it with others. Which is really my point - never think "This is not a duplicate!". Instead think "Why did this get closed as a duplicate? What am I missing?". To answer these questions you need to talk to others.) $\endgroup$
    – user1729
    Aug 6, 2021 at 9:17

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