Question

(p-10q)(pq+25)+5(50q-5p)

Answer 1

(p-10q)(pq+25)+5(50q-5p)=
=(p-10q)(pq+25)-25(p-10q)=
=(p-10q)((pq+25)-25)=(p-10q)(pq+25-25)=
=(p-10q)*pq=p^2q-10pq^2