Q:

Can I post same question again? 

After I posted a math question, if I did not receive the answer that I expected, can I post the question again?  
I think if I modify original question more concrete, I can expect better answer. 

A:

Posting the same/similar question again is discouraged.  If you post the same question again, almost surely, it will be closed as a duplicate of your original question. 
Here are couple of suggestions, if you want your question to garner attention (or) get better answers. 
$1$. You can edit the initial question and add more details.  Also, editing the question bounces your question to the first page. 
$2$. You can set a bounty for the question.  Questions with bounty associated will also be listed on the featured tab.