把多项式-y³+2xy²+3x³-4x²y按x的降幂排列,并求当x=-2,y=2分之1时这个多项式的值.
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![把多项式-y³+2xy²+3x³-4x²y按x的降幂排列,并求当x=-2,y=2分之1时这个多项式的值.](/uploads/image/z/3738404-20-4.jpg?t=%E6%8A%8A%E5%A4%9A%E9%A1%B9%E5%BC%8F-y%26%23179%3B%2B2xy%26%23178%3B%2B3x%26%23179%3B-4x%26%23178%3By%E6%8C%89x%E7%9A%84%E9%99%8D%E5%B9%82%E6%8E%92%E5%88%97%2C%E5%B9%B6%E6%B1%82%E5%BD%93x%3D-2%2Cy%3D2%E5%88%86%E4%B9%8B1%E6%97%B6%E8%BF%99%E4%B8%AA%E5%A4%9A%E9%A1%B9%E5%BC%8F%E7%9A%84%E5%80%BC.)
把多项式-y³+2xy²+3x³-4x²y按x的降幂排列,并求当x=-2,y=2分之1时这个多项式的值.
把多项式-y³+2xy²+3x³-4x²y按x的降幂排列,并求当x=-2,y=2分之1时这个多项式的值.
把多项式-y³+2xy²+3x³-4x²y按x的降幂排列,并求当x=-2,y=2分之1时这个多项式的值.
按x的降幂排列
原式=3x³-4x²y+2xy²-y³
=3*(-8)-4*4*1/2+2*(-2)*1/4-1/8
=-265/8
=3x^3-4x^2y+2xy^2-y^3