5 The function f is defined by
$$\mathrm { f } : x \mapsto x ^ { 2 } + 1 \text { for } x \geqslant 0$$
- Define in a similar way the inverse function \(\mathrm { f } ^ { - 1 }\).
- Solve the equation \(\operatorname { ff } ( x ) = \frac { 185 } { 16 }\).