\(\mathbf { 1 }\) The matrices \(\mathbf { A }\) and \(\mathbf { B }\) are given by \(\mathbf { A } = \left( \begin{array} { l l } 2 & 1
3 & 2 \end{array} \right)\) and \(\mathbf { B } = \left( \begin{array} { c c } a & - 1
- 3 & - 2 \end{array} \right)\).
- Given that \(2 \mathbf { A } + \mathbf { B } = \left( \begin{array} { l l } 1 & 1
3 & 2 \end{array} \right)\), write down the value of \(a\). - Given instead that \(\mathbf { A B } = \left( \begin{array} { l l } 7 & - 4
9 & - 7 \end{array} \right)\), find the value of \(a\).
\end{itemize}