(x-y分之1)除以(y-x分之1)
问题描述：
(x-y分之1)除以(y-x分之1)
答
（x-1/y）/（y-1/x）
(xy/y-1/y)/(xy/x-1/x)
=(xy-1)/y÷[(xy-1)/x]
=(xy-1)/y*[x/[(xy-1)]
=x/y