若1/x-1/y=3,试求分式（2x-2002xy-2y)/(x+2xy-y)的值

1/x-1/y=3
y-x=3xy
x-y=-3xy

（2x-2002xy-2y)/(x+2xy-y)
=(2*(-3xy)-2002xy)/(-3xy+2xy)
=-2008xy/(-xy)
=2008

1/x-1/y=3
(y-x)/xy=3
y-x=3xy
（2x-2002xy-2y)/(x+2xy-y)
=(2(x-y)-2002xy)/((x-y)+2xy)
=(-6xy-2002xy)/(-xy)
=2008

化简整体代入就可以了!