Using the definition of the derivative, find the derivative of f(x) = 1/(x-3)^2

ok so first I am using the equation f(x+h)-f(x)/h

I start out with (1/(x-3)^2 +h)-1/(x-3)^2 all of that over h. then i get a common denominator for (1/(x-3)^2 +h). Then I realize something is definitely wrong. Please help me.