4 You are given the system of equations
$$\begin{array} { r }
a ^ { 2 } x - 2 y = 1
x + b ^ { 2 } y = 3
\end{array}$$
where \(a\) and \(b\) are real numbers.
- Use a matrix method to find \(x\) and \(y\) in terms of \(a\) and \(b\).
- Explain why the method used in part (a) works for all values of \(a\) and \(b\).