x^3+x^2y-xy^2-y^3=0
x^2(x+y)-y^2(x+y)=0
(x+y)(x^2-y^2)=0
(x+y)(x+y)(x-y)=0
(x+y)^2 (x-y)=0
所以x=y,或x=-y
不懂发消息问我.(是不是还有什么条件?)