11.
The function f is defined by
$$\mathrm { f } ( x ) = \frac { 12 x } { 3 x + 4 } \quad x \in \mathbb { R } , x \geqslant 0$$
- Find the range of f.
- Find \(f ^ { - 1 }\).
- Show, for \(x \in \mathbb { R } , x \geqslant 0\), that
$$\mathrm { ff } ( x ) = \frac { 9 x } { 3 x + 1 }$$
- Show that \(\mathrm { ff } ( x ) = \frac { 7 } { 2 }\) has no solutions.