m^3(m-2n)+n^3(2m-n)

问题描述:

m^3(m-2n)+n^3(2m-n)

展开得
m^4-n^4-2m^3n+2mn^3
=(m^2+n^2)(m^2-n^2)-2mn(m^2-n^2)
=(m-n)^2(m^2-n^2)