This is my first meta post. I want to ask about one of my deleted post. In that post, I asked for a hint to some problem and gave reasons(brief) why I wasn’t able to solve that problem. To avoid speculation, following is the post:

Let $Y$ be compact and $f: Y\to Y$ continuous. Prove that there exists a non empty closed set $A\subseteq Y$ such that $A=f(A)$.

I saw this problem in James Dugundji topology book. Can anyone give some(tiny) hint to solve this problem?

Edit: I don’t know how to solve this “kind” of problem, showing two sets are equal, $A=f(A)$. First(& only) thing coming to mind is $f(Y)$ is compact, $A$ is compact since $A$ is closed in $Y$, $f(A)$ is also compact.

This post got 3 upvote. And answer to that post was also hint(one line). But later that post got deleted by ……… I have some post which are closed, some have net downvote, but those post didn’t get deleted. To be fair, those post have different nature of question than asking hint. So is it appropriate to ask for hint?


1 Answer 1


The idea behind this forum is to get authoritative answers to specific questions. So, simply asking for a hint is inappropriate (a hint can hardly be seen as an authoritative answer), and more so if that question has already been asked before and it got a complete answer. Note that, if this is the case, the complete answer, if it exists, can also be seen as a hint; simply read part of it and try to do the rest yourself.

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    $\begingroup$ I agree with the core of this answer, but it's worth mentioning that a well done hint is very different from the first steps of an authoritative answer. The former usually helps the questioner reframe the question; the latter is usually just small picture details. Hinting doesn't fit well with our main mission here, but it can bea really useful teaching tool. $\endgroup$
    – JonathanZ
    Apr 30, 2022 at 15:17
  • $\begingroup$ “Authoritative” is a subjective term. “Authoritative answer” is that your opinion or it is an official rule/law of SE website? So in conclusion you’re saying(indirectly) “ask for answer not hint”. You could have closed that post. Why you choose to delete it? Maybe I should ask, what’s difference between closed and delete a post? $\endgroup$
    – user264745
    Apr 30, 2022 at 15:48
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    $\begingroup$ @user264745 This is not my opinion. It's part of the StackExchange philosophy from the start. If you want just a hint, enter an appropriate chatroom and ask for a hint there. The assertion “You could have closed that post” is weird, since I did close the post, right?! And the post got deleted (not only by me) because it was a closed post that added no value to the site. $\endgroup$ Apr 30, 2022 at 16:00
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    $\begingroup$ @user264745: If you have taken the site tour, you will have been exposed to the StackExchange approach to asking and answering. More advice can be found in the Help Center. $\endgroup$
    – hardmath
    Apr 30, 2022 at 16:10
  • $\begingroup$ @hardmath no. I haven’t taken any site “tour”. $\endgroup$
    – user264745
    Apr 30, 2022 at 16:13
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    $\begingroup$ @user264745: Here is the site tour for Math.SE. $\endgroup$
    – hardmath
    Apr 30, 2022 at 16:14

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