先化简在求值;(-1/3XY)²×[xy(2x-y)-2x(xy-y)²],其中X=-2/3,Y=2
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先化简在求值;(-1/3XY)²×[xy(2x-y)-2x(xy-y)²],其中X=-2/3,Y=2
我算的是-7
我算的是-7
![先化简在求值;(-1/3XY)²×[xy(2x-y)-2x(xy-y)²],其中X=-2/3,Y=2](/uploads/image/z/15104143-55-3.jpg?t=%E5%85%88%E5%8C%96%E7%AE%80%E5%9C%A8%E6%B1%82%E5%80%BC%3B%28-1%2F3XY%29%26%23178%3B%C3%97%5Bxy%282x-y%29-2x%28xy-y%29%26%23178%3B%5D%2C%E5%85%B6%E4%B8%ADX%3D-2%2F3%2CY%3D2)
(-1/3xy)²×[xy(2x-y)-2x(xy-y)²]
=1/9x²y²×[2x²y-xy²-2x(x²y²-2xy²+y²)]
=1/9x²y²×[2x²y-xy²-2x³y²+4x²y²-2xy²]
=1/9x²y²×[2x²y-2x³y²+4x²y²-3xy²]
=1/9x³y³×[2x-2x²y+4xy-3y]
=1/9×(-2/3)³×2³×[2×(-2/3)-2×(-2/3)²×2+4×(-2/3)×2-3×2]
=1/9×(-8/27)×8×[-4/3-16/9-16/3-6]
=-64/3×(-130/9)
=8320/27
再问: 第二步算错了 应该是(-1/3xy)²×[xy(2x-y)-2x(xy-y)²] =1/9x²y²×[2xy-xy-2x(x²y²-y²)]
再答: 不对,是: (-1/3xy)²×[xy(2x-y)-2x(xy-y)²] =1/9x²y²×[2x²y-xy²-2x(x²y²-2xy²+y²)]
=1/9x²y²×[2x²y-xy²-2x(x²y²-2xy²+y²)]
=1/9x²y²×[2x²y-xy²-2x³y²+4x²y²-2xy²]
=1/9x²y²×[2x²y-2x³y²+4x²y²-3xy²]
=1/9x³y³×[2x-2x²y+4xy-3y]
=1/9×(-2/3)³×2³×[2×(-2/3)-2×(-2/3)²×2+4×(-2/3)×2-3×2]
=1/9×(-8/27)×8×[-4/3-16/9-16/3-6]
=-64/3×(-130/9)
=8320/27
再问: 第二步算错了 应该是(-1/3xy)²×[xy(2x-y)-2x(xy-y)²] =1/9x²y²×[2xy-xy-2x(x²y²-y²)]
再答: 不对,是: (-1/3xy)²×[xy(2x-y)-2x(xy-y)²] =1/9x²y²×[2x²y-xy²-2x(x²y²-2xy²+y²)]
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