1.
For a suitably chosen real constant aa, let a function f:R{a}Rf: \mathbb{R} - \{-a\} \to \mathbb{R} be defined by f(x)=axa+xf(x) = \frac{a-x}{a+x}. Further suppose that for any real number xax \neq -a and f(x)af(x) \neq -a, (ff)(x)=x(f \circ f)(x) = x. Then f(12)f\left(-\frac{1}{2}\right) is equal to: