m-n+2=2mn m-n 7p+q+p-7q=

(m-n) ^2+4mn m^2-2mn+n^2+4mn (m+n) ^2-=-=- 2mn (m-n) 2mn (m-n) 2mn (m-n) 7p+q p-7q 7p+q 7q-p 7pq+q^2+7pq-p^2 (q-p) (q+p)+14pq-+-=-+-=-=-p (p-q) q (q-p) p (p-q) q (p-q) pq (p-q) pq (p-q)