已知1÷x-1÷y=-3,则(5x+xy-5y)÷(x-xy-y)的值为( )
问题描述:
已知1÷x-1÷y=-3,则(5x+xy-5y)÷(x-xy-y)的值为( )
答
1÷x-1÷y=-3
则(y-x)÷(xy)=-3
所以y-x=-3xy
所以x-y=3xy
(5x+xy-5y)÷(x-xy-y)
=(5(x-y)+xy)÷((x-y)-xy)
=(15xy+xy)÷(3xy-xy)
=16xy÷(2xy)
=8