已知1/x=1/y+3,则(5x+xy-5y)/(x-xy-y)的值为( )

问题描述:

已知1/x=1/y+3,则(5x+xy-5y)/(x-xy-y)的值为( )
1个回答 分类:数学 2014-11-21

问题解答:

我来补答
1/x-1/y=3
(y-x)/xy=3
y-x=3xy
x-y=-3xy
(5x+xy-5y)/(x-xy-y)
=[5(x-y)+xy][(x-y)-xy]
=(-15xy+xy)/(-3xy-xy)
=-14xy/(-4xy)
=7/2
 
 
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