1. The problem statement, all variables and given/known data y = 2x / (1+x^2)^2 Find dy/dx 2. Relevant equations Chain rule 3. The attempt at a solution I completely forgot how to apply the chain rule.. I mean, I can always apply the quotient rule, but I'm sure this is 1000 times easier if you can apply the chain rule. Do you do something like u = 1+x^2 du = 2x so y = du/u But I may be getting confused with substitution rule with integration.. it's been a while since I touched calculus.. any suggestions?