少了个x
5x²y-[2x²y-(3xy-xy²)-3x²]-2xy²-y²
=5x²y-[2x²y-3xy+xy²-3x²]-2xy²-y²
=5x²y-2x²y+3xy-xy²+3x²-2xy²-y²
=3x²y-3xy²+3x²-y²+3xy
x=-3,y=-7
则
原式=-3*9*7+3*3*49+3*9-49+3*3*7=293
祝学习进步
5x²y-[2²y-(3xy-xy²)-3x²]-2xy²-y
1个回答
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