Question

Find the adjoint of the following matrix.
$\left[\begin{array}{cc}1& 3\\ -2& 4\end{array}\right]$

Answer 1

$A=\left[\begin{array}{cc}1& 3\\ -2& 4\end{array}\right]$

Here, $C_{11}=4$

$C_{12}=-(-2)=2$

$C_{21}=-3$

$C_{22}=1$

Hence, $adjA=\left[\begin{array}{cc}{C}_{11}& C_{21}\\ C_{12}& C_{22}\end{array}\right]=\left[\begin{array}{cc}4& -3\\ 2& 1\end{array}\right]$