We get done with just 3 matrices, because, in our examples, one entry is 1. But, generally, $\begin{bmatrix}
1 & 0 \\
0 & c \\
\end{bmatrix}
\begin{bmatrix}
b & 0 \\
0 & 1 \\
\end{bmatrix}
\begin{bmatrix}
1 & 0 \\
\frac{d}{c} & 1 \\
\end{bmatrix}
\begin{bmatrix}
0 & 1 \\
1 & 0 \\
\end{bmatrix}
=
\begin{bmatrix}
0 & b \\
c & d \\
\end{bmatrix}$