已知1/x-1/y=2,求3x+xy-3y/y-xy-x的值

已知1/x-1/y=2,求3x+xy-3y/y-xy-x的值
已知1/x-1/y=2,求3x+xy-3y/y-xy-x的值

已知1/x-1/y=2,求3x+xy-3y/y-xy-x的值
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

1/x-1/y=(y-x)/xy=2
y-x=2xy
x-y=-2xy
原式=[3(x-y)+xy]/[(y-x)-xy)]
=[3(-2xy)+xy]/[(2xy)-xy)]
=-5xy/xy
=-5