解:|x+2|+(y-1/2)²=0x+2=0 y-1/2=0x=-2 y=1/2于是原式=1/3x³-2x²y+2/3x³+3x²y+5xy²+7-5xy²=1/3x³+2/3x³+3x²y-2x²y+5xy²-5xy²+7=x³+x²y+7=(-2)³+(-2)²×(-1/2)+7=-8-2+7=-3