1) (a+b)*(a^2-ab+b^2) -2ab*(a+b)=(a+b)*(a^2-ab+b^2-2ab)=(a+b)*(a^2-3ab+b^2)
2) (x-y)*(x^2+xy+y^2)+8xy(x-y)=(x-y)*(x^2+xy+y^2+8xy)=(x-y)*(x^2+9xy+y^2)
3) (m-n)*(m^2+mn+n^2)-6m(m^2+mn+n^2)=(m^2+mn+n^2)*(m-n-6m)=(m^2+mn+n^2)*(-5m-n)
4) (p+q)*(p^2-pq+q^2)-2pq(p^2-pq+q^2)=(p^2-pq+q^2)*(p+q-2pq)=(p^2-pq+q^2)*(p-q)^2