4x²+2x+7+3x-8x²-2=4x²-8x²+2x+3x+7-2=-4x²+5x+56x²y+2xy-8x²y-4x-5xy+2y²x²-6x²y=6x²y-8x²y-6x²y+2xy-5xy-4x+2y²x²=-8x²y-4x-3x...还有两个。。不好意思啦~xy²-1/5xy²-3x²y+2x²y+3xy²-2xy²xy²-1/5xy²=4/5xy²-3x²y+2x²y+3xy²-2xy²=-x²y+xy²