(x+y)的立方-(x+y)的平方*(x+y)=(x+y)的立方-(x+y)的立方=0 你的题目是不是错了，是不是下面的题目：(x+y)的立方-(x-y)的平方*(x+y)=（x+y)[(x+y)²-(x-y)²]=(x+y)(x+y+x-y)(x+y-x+y)=4xy(x+y) (x+y)³-(x+y)²*(x-y)=(x+y)²(x+y-x+y)=2y(x+y)²
