已知x-y=6,xy=-8,求多项式(2x+3y-2xy)-(x+4y+xy)-(3xy+2y-2x)的值.她想如果通过
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已知x-y=6,xy=-8,求多项式(2x+3y-2xy)-(x+4y+xy)-(3xy+2y-2x)的值.她想如果通过x-y=6,xy=-8把x、y的值求出来,再把x、y的值代人多项式中就可以求出答案了,可是想了好半天,你能帮他想一个先不求x、y的值,试试看!
![已知x-y=6,xy=-8,求多项式(2x+3y-2xy)-(x+4y+xy)-(3xy+2y-2x)的值.她想如果通过](/uploads/image/z/9965863-55-3.jpg?t=%E5%B7%B2%E7%9F%A5x-y%3D6%2Cxy%3D-8%2C%E6%B1%82%E5%A4%9A%E9%A1%B9%E5%BC%8F%EF%BC%882x%2B3y-2xy%29-%28x%2B4y%2Bxy%29-%283xy%2B2y-2x%29%E7%9A%84%E5%80%BC.%E5%A5%B9%E6%83%B3%E5%A6%82%E6%9E%9C%E9%80%9A%E8%BF%87)
(2x+3y-2xy)-(x+4y+xy)-(3xy+2y-2x)
=2x+3y-2xy-x-4y-xy-3xy-2y+2x
=(2x-x+2x)+(3y-4y-2y)-(2xy+xy+3xy)
=3x-3y-6xy
=3(x-y)-6xy
把x-y=6,xy=-8代入得
3(x-y)-6xy
=3*6-6*(-8)
=18+48
=66
=2x+3y-2xy-x-4y-xy-3xy-2y+2x
=(2x-x+2x)+(3y-4y-2y)-(2xy+xy+3xy)
=3x-3y-6xy
=3(x-y)-6xy
把x-y=6,xy=-8代入得
3(x-y)-6xy
=3*6-6*(-8)
=18+48
=66
已知x-y=6,xy=-8,求多项式(2x+3y-2xy)-(x+4y+xy)-(3xy+2y-2x)的值.她想如果通过
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