Which of the following functions has a removable discontinuity at x=1x=1x=1?
f(x)=1x−1f(x) = \frac{1}{x-1}f(x)=x−11
f(x)=x2−1x−1f(x) = \frac{x^2-1}{x-1}f(x)=x−1x2−1
f(x)=1(x−1)2f(x) = \frac{1}{(x-1)^2}f(x)=(x−1)21
f(x)=x+1x−1f(x) = \frac{x+1}{x-1}f(x)=x−1x+1