The problem statement, all variables and given/known data Find y' .... X^2+y^2=25 I understand (I think) implicit differentiation, but there is one issue which hangs me up. I've done this before and this is just a refresher as my last calculus course was four years ago. From what I understand, 2x+2y(y')=0 But why isn't it 2x+2y(y^2)=0. ? Sorry for not using the notation format but I'm in a bit of a rush.