Question

Find adjoint of each of the matrices. $\begin{bmatrix}1&2\\\3&4\end{bmatrix}$

Answer 1

Let A=$\begin{bmatrix}1&2\\\3&4\end{bmatrix}$

we have A11=4, A12=-3, A21=-2, A22=1

so adj A=$\begin{bmatrix}A_{11}&A_{12}\\\A_{21}&A_{22}\end{bmatrix}$

=$\begin{bmatrix}4&-2\\\\-3&1\end{bmatrix}$