Firstly I would like to apologize for not knowing what forum to post this in. I am taking a calculus class but I am pretty sure this is not calculus.

Also I would like to note that this is my first proof based math class so this is all very new to me.

Here's the problem:

Let 'a' be a member of the real number set. Prove that a has a real square root if and only if a >or= 0.

I don't want the answer. I want help on how to do this problem so that hopefully I can do the entire problem set.

Thanks