Question

Find the adjoint of the given matrix :

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

Answer 1

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

We have,

$A_{11}=4,A_{12}=-3,A_{21}=-2,A_{22}=1$

Therefore,

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