For f(x)=x−1x+1f(x) = \frac{x-1}{x+1}f(x)=x+1x−1, what is the value of f(f(x))f(f(x))f(f(x))?
xxx
1x\frac{1}{x}x1
−1/x-1/x−1/x
x−1x+1\frac{x-1}{x+1}x+1x−1