7 The functions \(f , g\) and \(h\) are defined as follows.
$$\mathrm { f } ( x ) = 2 x \quad \mathrm {~g} ( x ) = x ^ { 2 } \quad \mathrm {~h} ( x ) = x + 2$$
Find each of the following as functions of \(x\).
- \(\mathrm { f } ^ { 2 } ( x )\),
- \(\operatorname { fgh } ( x )\),
- \(\mathrm { h } ^ { - 1 } ( x )\).