Well exams in 2 days and i forgot how to factorise. I decided to do some examples from da book and i saw this one

Factorise

4(p-q) + (p-q)^3 (^ = to the power btw:P)

I checked the back and it told me that the answer is (p-q)[4+(p-q)^2] That makes no sense whatsoever anyway we would left with pq^2 and qp^2 ffs i need an A badly and this question is making me nuts help ?!