Query about question "For which values of $x$ is the following..." [668]

GRE GRE Quant Problem Solving
1

https://www.gregmat.com/problems/quant?problem=for-which-values-of-x-is-the-fo
Here (x-1) cancels out in denominator and numerator. Shouldn’t f(x) be defined at 1

2

Consider the original expression.