请采纳
(y-x)^3=-（x-y）^3所以-3(x-y)^2-(y-x)^3=-3(x-y)^2+(x-y)^3=（x-y）^2[-3+(x-y)]即-3(x-y)^2-(y-x)^=（x-y）^2（x-y-3）
(x-y)²(x-y-3)
看
