(x的2次方-1)分之3x÷(1-(x+1)分之1)
问题描述：
(x的2次方-1)分之3x÷(1-(x+1)分之1)
答
=3x/(x+1)(x-1)÷(x+1-1)/(x+1)
=3x/(x+1)(x-1)×(x+1)/x
=3/(x-1)