[1/(x-1 - 1/(x+1）]÷ x/(x^2-1)
=[(x+1)-(x-1)]/(x+1)(x-1)*[(x+1)(x-1)/x]
=[2/(x+1)(x-1)]*[(x+1)(x-1)/x]
=2/xx的平方-1可以化简成什么？(x+1)(x-1)喔喔！谢谢哈~