-(x²-2xy+2y²﹚+[﹣3xy-2﹙x²-y﹚],其中x=﹣1,y=2先简化再求值
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![-(x²-2xy+2y²﹚+[﹣3xy-2﹙x²-y﹚],其中x=﹣1,y=2先简化再求值](/uploads/image/z/571626-18-6.jpg?t=-%28x%26%23178%3B%EF%BC%8D2xy%EF%BC%8B2y%26%23178%3B%EF%B9%9A%EF%BC%8B%5B%EF%B9%A33xy%EF%BC%8D2%EF%B9%99x%26%23178%3B%EF%BC%8Dy%EF%B9%9A%5D%2C%E5%85%B6%E4%B8%ADx%EF%BC%9D%EF%B9%A31%2Cy%EF%BC%9D2%E5%85%88%E7%AE%80%E5%8C%96%E5%86%8D%E6%B1%82%E5%80%BC)
-(x²-2xy+2y²﹚+[﹣3xy-2﹙x²-y﹚],其中x=﹣1,y=2先简化再求值
-(x²-2xy+2y²﹚+[﹣3xy-2﹙x²-y﹚],其中x=﹣1,y=2
先简化再求值
-(x²-2xy+2y²﹚+[﹣3xy-2﹙x²-y﹚],其中x=﹣1,y=2先简化再求值
原式=-x²+2xy-2y²﹣3xy-2x²+2y
=-3x²-xy-2y²+2y
=-3+2-8+4
=-5
原式=-x²+2xy-2y²-3xy-2x²+2y
=-3x²-xy-2y²+2y
代入=-5
-(x²-2xy+2y²﹚+[﹣3xy-2﹙x²-y﹚],其中x=﹣1,y=2
=-x²+2xy-2y²+[-3xy-2x²+2y]
=-x²+2xy-2y²-3xy-2x²+2y
=(-1-2)x²+(2-3)xy-2y²+2y
=-3x²+(-...
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-(x²-2xy+2y²﹚+[﹣3xy-2﹙x²-y﹚],其中x=﹣1,y=2
=-x²+2xy-2y²+[-3xy-2x²+2y]
=-x²+2xy-2y²-3xy-2x²+2y
=(-1-2)x²+(2-3)xy-2y²+2y
=-3x²+(-xy)-2y²+2y
=-3x²-xy-2y²+2y
-3x²-xy-2y²+2y
=-3*(-1)²-(-1)*2-2*2²+2*2
=-3-(-2)-8+4
=-1-8+4
=-9+4
=-5
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