已知x+y=5,xy=1求2x³y+4x²y²+2xy³先化简,再求值2(x-1)(x+2)-(3+x)(3-x),其中x=2
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![已知x+y=5,xy=1求2x³y+4x²y²+2xy³先化简,再求值2(x-1)(x+2)-(3+x)(3-x),其中x=2](/uploads/image/z/1611929-65-9.jpg?t=%E5%B7%B2%E7%9F%A5x%2By%3D5%2Cxy%3D1%E6%B1%822x%26%23179%3By%2B4x%26%23178%3By%26%23178%3B%2B2xy%26%23179%3B%E5%85%88%E5%8C%96%E7%AE%80%2C%E5%86%8D%E6%B1%82%E5%80%BC2%28x-1%29%28x%2B2%29-%283%2Bx%29%283-x%29%2C%E5%85%B6%E4%B8%ADx%3D2)
已知x+y=5,xy=1求2x³y+4x²y²+2xy³先化简,再求值2(x-1)(x+2)-(3+x)(3-x),其中x=2
已知x+y=5,xy=1求2x³y+4x²y²+2xy³
先化简,再求值2(x-1)(x+2)-(3+x)(3-x),其中x=2
已知x+y=5,xy=1求2x³y+4x²y²+2xy³先化简,再求值2(x-1)(x+2)-(3+x)(3-x),其中x=2
两个问题?
1、2x³y+4x²y²+2xy³=2xy(x²+2xy+y²)=2xy(x+y)²=2×1×5²=50
2、2(x-1)(x+2)-(3+x)(3-x)=2(x²+x-2)-(9-x²)=3x²+2x-13=3×2²+2×2-13=3