若x分之1-y分之1=1,求x-xy-y分之3y-xy-3x的值.

网友回答

(1/x)-(1/y)=1
两边同乘以xy
得y-x=xy,
x-xy-y/3y-3x-xy=-2xy/2xy=-1
======以下答案可供参考======
供参考答案1:
1/x-1/y=1
y-x=xy
x-y=-xy
(3y-xy-3x)/(x-xy-y)
=(3xy-xy)/(-xy-xy)
=2xy/(-2xy)
=-1