4（x-y）三次方-2y（y-x）平方
=4(x-y)^3-2y(x-y)^2
=(x-y)^2(4x-4y-2y)
=(x-y)^2(4x-6y)
=2(2x-3y)(x-y)^2
3m（m-n）平方-6n（n-m）
=3m(m-n)^2+6n(m-n)
=(m-n)(3m(m-n)+6n)
=(m-n)(3m^2-3mn+6n)
=3(m-n)(m^2-mn+2n)
8a（x-y）三次方-b（y-x）平方
=8a(x-y)^3-b(x-y)^2
=(x-y)^2(8a(x-y)-b)
=(x-y)^2(8ax-8ay-b)