求整式-6x²y加上2x³-xy²+7y³的和与-7x²y+2x³-xy²-y³的差

来源：学生作业学帮网编辑：学帮网时间：2024/06/17 00:54:59

-6x²y+2x³-xy²+7y³-(-7x²y+2x³-xy²-y³)
=-6x²y+2x³-xy²+7y³+7x²y-2x³+xy²+y³
=8y³+x²y

-6x²y+(2x³-xy²+7y³)-(-7x²y+2x³-xy²-y³)
　　=-6x²y+2x³-xy²+7y³+7x²y-2x³+xy²+y³
　　=8y³+x²y