Find derivative of ((-6x)/(x^2+3)^2)) I can't seem to figure out how to do the simplification part of it so please show that work.?

f(x) = ((-6x)/(x^2+3)^2))
f ' = [(x^2+3)^2)) (-6) - (-6x)(2)(x^2+3)(2x)] / (x^2+3)^4 <<< factor numerator
f ' = (x^2+3)[(-6)(x^2+3) + (24x^2)] / (x^2+3)^4 <<< cancel
f ' = (18x^2 -18)/(x^2+3)^3 <<< answer