14.
\(\displaystyle A =
\begin{pmatrix}
1 & 2 \\
3 & 4
\end{pmatrix}\)
15.
\(\displaystyle A =
\begin{pmatrix}
6 & 3 \\
-4 & -1
\end{pmatrix}\)
16.
\(\displaystyle A =
\begin{pmatrix}
3 & -7 \\
-2 & 5
\end{pmatrix}\)
17.
\(\displaystyle A =
\begin{pmatrix}
8 & 7 \\
2 & 2
\end{pmatrix}\)
18.
\(\displaystyle A =
\begin{pmatrix}
-3 & 4 \\
-2 & 5
\end{pmatrix}\)
19.
\(\displaystyle A =
\begin{pmatrix}
3 & 2 \\
4 & 3
\end{pmatrix}\)
20.
\(\displaystyle A =
\begin{pmatrix}
4 & 0 \\
0 & -3
\end{pmatrix}\)
21.
\(\displaystyle A =
\begin{pmatrix}
1 & 2 \\
-3 & -6
\end{pmatrix}\)