=(x+y)^4 (x+y) -x^3 -y^2
={(x+y)^2}^2(x+y) -x^3 -y^2
=(x^2+2xy+y^2)^2 (x+y) - x^3 -y^2
=(x^2+2xy)^2 + 2(x^2+2xy)y^2- x^3 -y^2
={x^4+ 4x^3y+(2xy)^2+2(x^2+2xy)y^2- x^3 -y^2
太麻烦了差不多了自己按着后面的做吧