Shortcut for calculating eigenvalues

[Kevin_McFarlane]

For 2x2 matrix see A quick trick for computing eigenvalues | Chapter 15, Essence of linear algebra

So for the eigenvalues in 3, m = average of the diagonals (the trace). p is the determinant. You can verify those values for the matrix shown in bottom right. Eigenvalues are 10 and 4 after plugging into the formula.

[TMosh]

Thanks for the information.