y=(x^2-2x+1)／(x^2-1)
=(x-1)^2/(x+1)(x-1)
=(x-1)/(x+1)
=(x+1-2)/(x+1)
=1-2/(x+1)
显然 ,2/(x+1) 可以取到不等于0的任何实数
所以,y=(x+1)/(x-1)的值域 是y≠ 1