Remark

For a square matrix of order 2, given by \(A = \begin{bmatrix} a_{11} & a_{12} \\ a_{21} & a_{22} \end{bmatrix}\). The adj A can also be obtained by interchanging \(a_{11}\) and \(a_{22}\) and by changing signs of \(a_{12}\) and \(a_{21}\), i.e., alt text We state the following theorem without proof.