Question

f: R -{-1}—> R-{-1},f(x) =1-x/1+x . Find fof.

Answer 1

$f(x) = \frac{1 - x}{1 + x} \\ fof = f(f(x)) \\ = \frac{1 - (\frac{1 - x}{1 + x} )}{1 + (\frac{1 - x}{1 + x}) } = \frac{(1 + x) - (1 - x)}{(1 + x) + (1 - x)} \\ = \frac{2x}{2} = x$