romsek Math Team Sep 2015 2,871 1,607 USA Nov 23, 2019 #2 $\Delta R$ is the determinant of the matrix on the left hand side. I'm sure you can read up on how to find the determinant of matrix.
$\Delta R$ is the determinant of the matrix on the left hand side. I'm sure you can read up on how to find the determinant of matrix.