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

问题描述:

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

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