Question

4m (n-m)^2-16m^2 (m-n)

Answer 1

$4m(n-m)^2-16m^2(m-n)=4m(n-m)^2+16m^2(n-m)=\\=4m(n-m)((n-m)+4m)=4m(n-m)(n+3m)$