先化简,再求值7a-2[3a²+(2+3a-a²)],其中a=-1(2x²y-2xy²)-(3x²y²+3x²y)+(3x²y²-xy²),其中x=-1,y=2已知:x-y=2,xy=-3,求代数式(2x+3y-2xy)-(x+4y+xy)-(3xy+2y-2x)
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![先化简,再求值7a-2[3a²+(2+3a-a²)],其中a=-1(2x²y-2xy²)-(3x²y²+3x²y)+(3x²y²-xy²),其中x=-1,y=2已知:x-y=2,xy=-3,求代数式(2x+3y-2xy)-(x+4y+xy)-(3xy+2y-2x)](/uploads/image/z/2581293-21-3.jpg?t=%E5%85%88%E5%8C%96%E7%AE%80%2C%E5%86%8D%E6%B1%82%E5%80%BC7a-2%5B3a%26%23178%3B%2B%282%2B3a-a%26%23178%3B%29%5D%2C%E5%85%B6%E4%B8%ADa%3D-1%EF%BC%882x%26%23178%3By-2xy%26%23178%3B%EF%BC%89-%EF%BC%883x%26%23178%3By%26%23178%3B%2B3x%26%23178%3By%29%2B%283x%26%23178%3By%26%23178%3B-xy%26%23178%3B%29%2C%E5%85%B6%E4%B8%ADx%3D-1%2Cy%3D2%E5%B7%B2%E7%9F%A5%EF%BC%9Ax-y%3D2%2Cxy%3D-3%2C%E6%B1%82%E4%BB%A3%E6%95%B0%E5%BC%8F%EF%BC%882x%2B3y-2xy%29-%28x%2B4y%2Bxy%29-%283xy%2B2y-2x%29)
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先化简,再求值7a-2[3a²+(2+3a-a²)],其中a=-1(2x²y-2xy²)-(3x²y²+3x²y)+(3x²y²-xy²),其中x=-1,y=2已知:x-y=2,xy=-3,求代数式(2x+3y-2xy)-(x+4y+xy)-(3xy+2y-2x)
先化简,再求值
7a-2[3a²+(2+3a-a²)],其中a=-1
(2x²y-2xy²)-(3x²y²+3x²y)+(3x²y²-xy²),其中x=-1,y=2
已知:x-y=2,xy=-3,
求代数式(2x+3y-2xy)-(x+4y+xy)-(3xy+2y-2x)
先化简,再求值7a-2[3a²+(2+3a-a²)],其中a=-1(2x²y-2xy²)-(3x²y²+3x²y)+(3x²y²-xy²),其中x=-1,y=2已知:x-y=2,xy=-3,求代数式(2x+3y-2xy)-(x+4y+xy)-(3xy+2y-2x)
原式=7a-2[3a^2+2+3a-a^2]=7a-2[2a^2+3a+2]=7a-4a^2-6a-4=a-4a^2-4,将a=-1代入,得-1-4×(-1)^2-4=-1-4-4=-9
原式=2x^2y-2xy^2-3x^2y^2-3x^2y+3x^2y^2-xy^2=-x^2y-3xy^2=-xy(x+3y),将x、y的值代入,得10
原式=2x+3y-2xy-x-4y-xy-3xy-2y+2x=3x-3y-6xy=3(x-y-2xy),将x、y的值代入,得24