Let f: R → R be defined as f(x)=x-1 and g: R -{1,-1} → R be defined as g(x)=x^2/(x^2-1). Then the function f ° g is:

Let $\displaystyle f: \mathbb{R} \rightarrow \mathbb{R}$ be defined as $\displaystyle f(x)=x-1$ and $\displaystyle g: \mathbb{R}-\{1,-1\} \rightarrow \mathbb{R}$ be defined as $\displaystyle g(x)=\frac{x^2}{x^2-1}$. Then the function $\displaystyle f \circ g$ is :