化简求值:2xy^2-[3xy^2-2(x^2y-(1/2)xy^2)]-2x^2y其中x=-2/3,y=-1/2
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化简求值:2xy^2-[3xy^2-2(x^2y-(1/2)xy^2)]-2x^2y其中x=-2/3,y=-1/2
2xy^2-[3xy^2-2(x^2y-(1/2)xy^2)]-2x^2y
=2xy²-[4xy²-2x²y]-2x²y
=2xy²﹣4xy²﹢2x²y﹣2x²y
=﹣2xy²
=﹣2×﹙﹣2/3﹚﹙﹣1/2﹚
=﹣2/3
再问: ﹣2×﹙﹣2/3﹚﹙﹣1/2﹚ (﹣1/2﹚不是平方吗
再答: 漏了 2xy^2-[3xy^2-2(x^2y-(1/2)xy^2)]-2x^2y =2xy²-[4xy²-2x²y]-2x²y =2xy²﹣4xy²﹢2x²y﹣2x²y =﹣2xy² =﹣2×﹙﹣2/3﹚﹙﹣1/2﹚² =1/3
=2xy²-[4xy²-2x²y]-2x²y
=2xy²﹣4xy²﹢2x²y﹣2x²y
=﹣2xy²
=﹣2×﹙﹣2/3﹚﹙﹣1/2﹚
=﹣2/3
再问: ﹣2×﹙﹣2/3﹚﹙﹣1/2﹚ (﹣1/2﹚不是平方吗
再答: 漏了 2xy^2-[3xy^2-2(x^2y-(1/2)xy^2)]-2x^2y =2xy²-[4xy²-2x²y]-2x²y =2xy²﹣4xy²﹢2x²y﹣2x²y =﹣2xy² =﹣2×﹙﹣2/3﹚﹙﹣1/2﹚² =1/3
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