I am from Brazil, this means that my vocabulary for english is very poor, in relation to my vocabulary in portuguese - which is my native languange. Sometimes when I ask stuff, I try to search some terms about my interest first and then I give up, sometimes people come up and say: "This is a duplicate" or "this was already asked before". When I read the title of the question given by MSE users, it's usually something I'd never think about asking. So I believe it's better to ask it, if someone points it as a duplicate I can vote to close or delete it.
As long as you made an honest effort to search first, there is no shame in asking what turns out to be a duplicate. In addition to the built-in search, you should try Google search with the operator
site:math.stackexchange.com -- it often brings up more relevant results.
It is usually better to leave duplicates in place, marked as such, instead of deleting them. Later, someone may also be looking for the keywords in the title of your version, as opposed to the answered version. By the way, I see only two duplicates among your questions, versus six closed for other reasons. So it does not look like you have a major duplication problem.