计算(x-y)(x²+2xy-3y²）

计算(x-y)(x²+2xy-3y²）
计算(x-y)(x²+2xy-3y²）

计算(x-y)(x²+2xy-3y²）
=(x-y)(x+3y)(x-y)
=（x+3y)(x-y)平方
若求展开式为
=X立方+X平方Y-5XY平方+3Y立方

是拆开还是干嘛？

=(x-y)((x^2+2xy+y^2)-4y^2)
=(x-y)((x-y)^2-4y^2)
=(x-y)(x-3y)(x+y)
=(x^2-y^2)(x-3y)
=x^3-3yx^2-xy^2+3y^3