1. The problem statement, all variables and given/known data Prove whether the function f(x) = x/(1+x^2) with domain & codomain = reals is one-to-one, onto, or both. 2. Relevant equations 3. The attempt at a solution I know to show if it's one-to-one I have to show a/(1+a^2) = b/(1+b^2), ultimately that a = b, I don't know how to simplify them to that.