题目打的不规范
我猜应该是2x/(x^2-1)-1/(x-1)
2x/(x^2-1)-1/(x-1)
=2x/[(x+1)(x-1)]-(x+1)/[(x+1)(x-1)]
=[2x-(x+1)]/[(x+1)(x-1)]
=(x-1)/[(x+1)(x-1)]
=1/(x+1)