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已知x-y=3,xy=-1,求(2x+3y-2xy)-(x+4y+xy)-(3xy+2y-2x)的值
人气:395 ℃ 时间:2019-10-09 08:29:15
解答
(2x+3y-2xy)-(x+4y+xy)-(3xy+2y-2x)
=2x+3y-2xy-x-4y-xy-3xy-2y+2x
=3x-3y-6xy
=3(x-y-2xy)
x-y=3,xy=-1代入=3*(3+2)=15
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