3x^2y-[2xy-2(xy-2/3x^2y)+xy]，其中x=3，y=-3/1.等于
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先化简，再求值
3x²y-[2xy-2(xy-2/3x²y)+xy]
=3x²y-2xy+2(xy-2/3x²y)-xy
=3x²y-2xy+2xy-4/3x²y-xy
=5/3x²y-xy
=xy(5/3x-1)
将x=3,y=-1/3 代入
原式=xy(5/3x-1)=3×(-1/3)(5/3×3-1)=-1×(5-1)=-4
希望能帮到你，祝学习进步
3x²y-[2xy-2(xy-2/3x²y)+xy]
=3x²y-2xy+2(xy-2/3x²y)-xy
=3x²y-2xy+2xy-4/3x²y-xy
=5/3x²y-xy
=xy(5/3x-1)
将x=3,y=-1/3 代入
原式=xy(5/3x-1)=3×(-1/3)(5/3×3-1)=-1×(5-1)=-4
希望能帮到你，祝学习进步
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3x²y-[2xy-2(xy-2/3x²y)+xy]
=3x²y﹣3x²y﹣xy
=﹣xy
=﹣3×﹙﹣1/3﹚
=1
=3x²y﹣3x²y﹣xy
=﹣xy
=﹣3×﹙﹣1/3﹚
=1
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∵x=3，y=-3/1(此处应为：y=-1/3)
3x^2y-[2xy-2(xy-2/3x^2y)+xy]=3x²y-2xy+2xy-4x²y/3-xy=5x²y/3-xy=5×3²×(-1/3)/3-3×(-1/3)=-5+1=-4
3x^2y-[2xy-2(xy-2/3x^2y)+xy]=3x²y-2xy+2xy-4x²y/3-xy=5x²y/3-xy=5×3²×(-1/3)/3-3×(-1/3)=-5+1=-4
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