3 In this question you must show detailed reasoning.
\(\mathbf { A }\) and \(\mathbf { B }\) are matrices such that \(\mathbf { B } ^ { - 1 } \mathbf { A } ^ { - 1 } = \left( \begin{array} { r r } 2 & 1
- 1 & 1 \end{array} \right)\).
- Find \(\mathbf { A B }\).
- Given that \(\mathbf { A } = \left( \begin{array} { l l } \frac { 1 } { 3 } & 1
0 & 1 \end{array} \right)\), find \(\mathbf { B }\).