Matrices And Determinants

Let \(A\) be a \(2 \times 2\) real matrix and \(I\) be the identity matrix of order 2. If the roots of the equation \(|\mathrm{A}-x \mathrm{I}|=0\) be \(-1\) and 3, then the sum of the diagonal elements of the matrix \(\mathrm{A}^2\) is