2 The functions f and g are defined for \(x \in \mathbb { R }\) by
$$\begin{aligned}
& \mathrm { f } : x \mapsto 3 x + a
& \mathrm {~g} : x \mapsto b - 2 x
\end{aligned}$$
where \(a\) and \(b\) are constants. Given that \(\mathrm { ff } ( 2 ) = 10\) and \(\mathrm { g } ^ { - 1 } ( 2 ) = 3\), find
- the values of \(a\) and \(b\),
- an expression for \(\mathrm { fg } ( x )\).