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已知1/x-1/y=2,求3x+xy-3y/y-xy-x的值
人气:277 ℃ 时间:2020-01-29 18:21:11
解答
1/x-1/y=2
(y-x)/xy=2
y-x=2xy
(3x+xy-3y)/(y-xy-x)
=[-3(y-x)+xy]/[(y-x)-xy]
=[(-6+1)xy]/[(2-1)xy]
=-5
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