Respuesta :

Factor the equation so... 
(r^2-pr) and (p^2q-pqr)

Factor out (r^2-pr) = r(r-p)
Factor out (p^2q-pqr) = pq(p-r)

Add a negative to r(r-p) to make it -r(p-r)

(pq-r)(p-r) is the answer...  I'm sorry I can't explain things well, but I tried.