5. Given that \(a\) and \(b\) are non-zero constants and that
$$\mathbf { X } = \left( \begin{array} { r r }
a & 2 b
- a & 3 b
\end{array} \right) ,$$
- find \(\mathbf { X } ^ { - 1 }\), giving your answer in terms of \(a\) and \(b\).
Given also that \(\mathbf { Z X } = \mathbf { Y }\), where \(\mathbf { Y } = \left( \begin{array} { c c } 3 a & b
a & 2 b \end{array} \right)\), - find \(\mathbf { Z }\), simplifying your answer.