计算:合并同类项2(x-y)²-3(x-y)³-(x-y)²+2(x-y)³-6(y-x)²原式=

问题描述:

计算:合并同类项
2(x-y)²-3(x-y)³-(x-y)²+2(x-y)³-6(y-x)²
原式=