Because solving mathematical problems is interesting, fun and it helps to keep mental acumen.
I also find my teaching abilities, and perhaps writing abilities, to improve much faster because of this site. Also my grasp of advanced set theoretical concepts.
Welcome to MSE
This is based a comment Arturo used to add to questions of relatively new users (although this post has been edited a few times and the message has been slightly modified):
Welcome to math.SE: since you are new, I wanted to let you know a few things about the site. In order to get the best possible answers, it is helpful if you say in what ...
I read a story about some guy who was deathly sick and to pass the time before he expired he began to read Euclid's Elements. Needless to say he made a miraculous recovery. I was also close to buying the farm so I joined a bunch of math forums and became a little active on a few here and guess what? I feel like a 85 year old again. Sharing what you have no ...
How to write math
This might be added as a pointer where to find help:
For some basic information about writing mathematics at this site see, e.g., here, here, here and here.
For some basic information about writing mathematics at this site see, *e.g.*, [here](/help/notation), [here](//math.meta.stackexchange.com/q/5020), [here](//meta.stackexchange.com/...
Congratulations Daniel Fischer for getting into the 100k club. Your clear explanations and helpful hints combined with your patient mentoring does not go unnoticed in the math chatroom. Also this accomplishment has not been mentioned.
Whenever I use a new program, get an error message or install a new hardware, I use google to find my problem on some forum where usually someone already answered it free of charge. This person will never even know that I was helped by the answer.
Whenever I have a question about language that is not well answered by my textbook or a question about ...
After you ask a question here, if you get an acceptable answer, you should "accept" the answer by clicking the check mark $\checkmark$ next to it. This scores points for you and for the person who answered your question. You can find out more about accepting answers here: How do I accept an answer?, Why should we accept answers?, What ...
Side complaint: I seem to be getting an awful lot of review audits, maybe one per five legitimate review requests.
If you are asking me to spend my time performing community service, I would prefer you not waste my time with pointless "fake" tasks.
There's something entertaining about answering questions that are hard enough to hold my interest but not so hard as to be a grueling experience. Also it's good to be helping students with math. I rarely use mathoverflow because the problems there are much harder and would take a while to solve if I even could. The problems in my field there often involve ...
The newest and one of the most ridiculous examples to date:
I failed this by clicking "add comment". That's right. You're not allowed to comment when you're being audited. I'm filing a bug report.
User Did has just hit 200K rep today, and the number of 200K+ users on Math S.E. is now three.
Congratulations for your fantastic achievement Did! Your dedication, enthusiasm, and insight are really inspiring. You worked hard, you deserve it, and now you have got it! Please accept our congratulations on this wonderful recognition of your merits. I wish you ...
This question is of insufficient quality (Template arose from this thread)
If necessary, this can be preceded by Hello, welcome to Math.SE.
Your question is phrased as an isolated problem, without any further information or context. This does not match many users' quality standards, so it may attract downvotes, or be put on hold. To prevent that, please [...
This question has recently been undeleted. I have to admit that I'm stunned.
There is nothing good about this Q&A: the questions consist a homework dump from a timed online quiz; they have apparently been copy-pasted here without any effort done to even format them correctly (the sentence "Answer both parts for full credit" is especially ...
I have failed a few. One interesting thing is that, for "close" audits at least, the system lies about the vote count, showing 0 instead of the actual vote count. Which seems to be counterproductive: it appears they change the vote count to encourage reviewers to evaluate the question independently, but then they criticize the reviewer being too independent ...
In 2010 a psychology graduate student did one or two surveys on motivation for people using, and especially answering, on MO, see http://tea.mathoverflow.net/discussion/890/mathoverflow-survey-update/ Tausczik eventually published her results in psychology journals. She had been an undergraduate math major at Berkeley when MO was still in its formative ...
More descriptive/informative titles
Please try to make the titles of your questions more informative. For example, Why does $a<b$ imply $a+c<b+c$? is much more useful for other users than A question about inequality.
From How can I ask a good question?: Make your title as descriptive as possible. In many cases one can actually phrase the title as ...
Here is my totally honest, non-high-flown answer:
I'm just trying to become better at math. Learning from a book and by homework exercises is not that interesting to me, but I really do enjoy teaching others. In addition, I find that I tend to give the clearest and most rigorous answers when I'm trying to explain something to someone who doesn't understand, ...
Congratulations to me, the first ever recipient of the highly-coveted big-list bronze tag badge. This goes on my CV, for sure.
EDIT–––Even more congratulations to me, for achieving a reputation of exactly 123,456. Just enjoying it while it lasts.
My answers on MathStackexchange are usually not too high level questions, simply because I'm not an expert in any math field.
Now I notice that when I write an answer it is mostly when I see the problem and think I can write a concise "cool" answer or apply a tool that surprised my when acquiring it. If you have an aha-moment, you feel like now you're the ...
This is not legitimate under the terms of the cc by-sa 3.0 with attribution required license used by StackExchange.
In fact it is a bait-and-switch style operation. Although one cannot tell it from the summary results returned by a Google search, per the OP's suggestion, the referenced web-site does not actually deliver the content that Google had spidered....
A new user who posts a pure homework question:
Another version of something to say to a new user who posts a pure homework question:
Context: I didn't actually know this thread was here, so I typed this up on the fly as something appropriate. Since someone who's been here way longer than I thought it would be useful here and suggested I post it here, I ...
Multiple questions in one post
Please ask only one question per post. Having multiple questions in the same post is discouraged and such posts may be put on hold, see meta.
Please ask only one question per post. Having multiple questions in the same post is discouraged and such posts may be put on hold, see [meta](https://math.meta.stackexchange.com/q/...
Tags that are frequently used incorrectly
Sum of Squares
The sums-of-squares tag is for questions about representations of integers as sums of squares, see the tag-wiki and relevant discussion on meta.
The ([tag:sums-of-squares]) tag is for questions about representations of integers as sums of squares, see the [tag-wiki](https://math.stackexchange.com/...
https://math.stackexchange.com/a/508096/17596 showed up as a "first post" review. I found the animation far more distracting than helpful, so I downvoted (disagreeing, apparently, with fifteen folks who think it's the cat's meow). Review audit failed.
I failed a review audit for this question because I went to close it as duplicate as I recognised the title and content of the post so thought it was an exact duplicate of itself (the review had artificially made it appear that the question was written 2 hours ago). This highlights a flaw in the system in my opinion.
Congratulations to Henning Makholm on reaching $100$K on $5$ March $2015$, bringing the number of $100$K+ users to a full score; not bad for someone who describes ‘[r]eal mathematics’ as ‘more of hobby’!
I always enjoy reading your answers, and not just on account of my particular mathematical interests.
Welcome/LaTeX help/Homework question
Something like this is useful when a new user asks what is almost surely a homework question without formatting anything into LaTeX.
Welcome to math.SE! Please consider taking the time to read the faq to familiarise yourself with some of our common practices. In addition, this page should give you a start at learning ...
Past congratulatory threads
This list was compiled by Martin Sleziak: all the credit goes to him. I merely reformatted it.
(ordered by id)
Congratulations, Brian M. Scott!
Congratulations, Did hits the 100K!!