First what we need to do is we need to think of what the question is asking us to find. In this case it is dy/dx but what is this. This is the rate of change of y with respect to x. For understanding purposes: To do this what we want to do is use our formal definition of a derivative with our limit as h tends to 0 for (f(x+h)-f(x))/h. We can then sub in our equation into this and find our answer.
Quicker Method: dy/dx of x^n=nx^n-1. We can then do this to every part of our function y to get an answer of 4x^3 +2x