Question
Write the adjoint of the matrix $\text{A}=\begin{bmatrix} -3 & 4 \\ 7 & -2 \end{bmatrix}$.

Answer

Let $C_{ij}$ be a cofactor of $a_{ij}​​​​​​​$​​​​​​​ in A.
Now, $C_{11} = -2 C_{12} = -7 C_{21} = -4 C_{22} = -3$
$\therefore\ \text{adj A}=\begin{bmatrix} -2 & -7 \\ -4 & -3 \end{bmatrix}^\text{T}=\begin{bmatrix} -2 & -4 \\ -7 & -3 \end{bmatrix}$

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