化简求值:3x2y-[2x2y-3(2xy-x2y)-xy],其中x=-1,y=-2

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收藏|2022/06/12 07:07

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2022/06/12 07:30

3x²y-[2x²y-3﹙2xy-x²y﹚-xy]=3x²y-[2x²y-6xy+3x²y-xy]=3x²y-[5x²y-7xy]=3x²y-5x²y+7xy=-2x²y+7xy=xy﹙-2x+7﹚把x=-1,y=-2代入上式得:=﹙-1﹚×﹙-2﹚[﹙-2﹚×﹙-1﹚+7]=2×[2+7]=2×9=18

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其他回答(1)
  • 3x²y-[2x²y-3(2xy-x²y)-xy]=3x²y-2x²y+3(2xy-x²y)+xy=x²y+(6xy-3x²y)+xy=-2x²y+7ab【x=-1,y=2】=-2(-1)²(-2)+7(-1)(-2)=4+14=18【x=-12,y=2】=-2(-12)²*2+7(-12)*2=-576-168=-744
    回答于 2022/06/12 07:43
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