7. Given that \(\mathbf { X } = \left( \begin{array} { c c } 2 & a
- 1 & - 1 \end{array} \right)\), where \(a\) is a constant, and \(a \neq 2\),
- find \(\mathbf { X } ^ { - 1 }\) in terms of \(a\).
Given that \(\mathbf { X } + \mathbf { X } ^ { - 1 } = \mathbf { I }\), where \(\mathbf { I }\) is the \(2 \times 2\) identity matrix,
- find the value of \(a\).