Can i post my article in arxiv for comments from other mathematicians?
The rules for submitting an article to Arxiv are fairly clear and do not exclude you on the basis of not being affiliated to a research institution. You have to be registered, but that's about it.

I feel that a change of terminology is in order - you don't "post" to Arxiv - it's a preprint server, not discussion forum or a message board. You "submit" work to Arxiv. Among the functions that a preprint server provides is a record of intellectual ownership. If you submit it to a preprint server, you could claim later on that this work is your own and was published on a certain date. A second function is that of peer review, which you are asking about here. If indeed your work was plagiarized, this would likely be discovered by peer reviewers if you submitted it to the Arxiv (or for that matter, to any journal with a reasonable editorial process).

Note that Arxiv does not have a peer-review process - it's a preprint server that exists specifically to speed up publication of non peer-reviewed research. However, it does have a moderation process. So while submitting your research to a preprint server makes it more likely to have it peer reviewed, it does not guarantee it.

So, to answer your question  


  Can i post my article in arxiv for comments from other mathematicians?


the answer is undoubtedly "yes". Nothing prevents you from doing this.

However, the corollary which is implied in your question:


  If I submit my article to Arxiv, will it be peer-reviewed by mathematicians?


is more difficult to answer. Almost all peer review is a volunteer activity, irrespective of where you submit, so someone needs to volunteer their time and intellect to reviewing your contribution.

Ask yourself what your motivations are. Do you want a publication, or do you want your contribution to objectively evaluated? Either way, submit it to the Arxiv to state that the work is yours.