若(1/x )-(1/y)=3,求(3x+4xy-3y)/(x-2xy-y)的值.
问题描述：
若(1/x )-(1/y)=3,求(3x+4xy-3y)/(x-2xy-y)的值.
答
(1/x )-(1/y)=3
∴y-x=3xy
(3x+4xy-3y)/(x-2xy-y)
=[3(x-y)+4xy]/[(x-y)-2xy]
=(-9xy+4xy)/(-3xy-2xy)
=1