4 The matrix \(\mathbf { A }\) is given by \(\mathbf { A } = \left( \begin{array} { l l } 1 & 1
3 & 5 \end{array} \right)\).
- Find \(\mathbf { A } ^ { - 1 }\).
The matrix \(\mathbf { B } ^ { - 1 }\) is given by \(\mathbf { B } ^ { - 1 } = \left( \begin{array} { r r } 1 & 1
4 & - 1 \end{array} \right)\). - Find \(( \mathbf { A B } ) ^ { - 1 }\).