1/x-1/y=3,则求3y+xy-3x/2x-xy-2y

1/x-1/y=3,则求3y+xy-3x/2x-xy-2y
1/x-1/y=3,则求3y+xy-3x/2x-xy-2y

1/x-1/y=3,则求3y+xy-3x/2x-xy-2y
y-x=3xy
（3y+xy-3x）/（2x-xy-2y）=10xy/(-7xy)=10/7

将一已知式，化简成Y-X=3XY，再把未知式的XY用Y-X代替，上下约分就好了