Mathematics - Functions Question with Solution | TestHub

$\begin{array}{rl}& fof(x)=\{\begin{array}{l}f(x);\text{ when }f(x)\text{ is rational }\\ 1-f(x)\text{; when }f(x)\text{ is irrational }\end{array}\\ & =\{\begin{array}{l}\mathrm{x};\text{ when }\mathrm{x}\text{ is rational }\\ 1-(1-\mathrm{x});\text{ when }\mathrm{x}\text{ is irrational }\end{array}=\mathrm{x}\\ & \end{array}$