题目是否为：（x-y）+(y-x)3?
若是,则解题如下：=（x-y）-(x-y)3
=(x-y){1-(x-y)2}
=(x-y){1-(x-y)}{1+(x-y)}
=(x-y)(1-x+y)(1+x-y)
备注：2表示平方 3表示立方