Compute the eigenvalues \color{red} \lambda_1 and
\color{blue} \lambda_2
of
\begin{pmatrix} A & B\\
C & D \end{pmatrix}
with {\color{red} \lambda_1} > \color{blue} \lambda_2.
\color{red} \lambda_1
=
L1
\color{blue} \lambda_2
=
L2
The eigenvalues are the roots of the characteristic polynomial
\det \begin{pmatrix} A - \lambda & B\\
C & D-\lambda \end{pmatrix}.
This is the quadratic equation
\left(A - \lambda \right) \left(D- \lambda \right) - negParens(B*CN)= 0 =
\lambda^2 -T \lambda + det.
We factorize \lambda^2 -T \lambda + det =
\left( \lambda - L1 \right) \left( \lambda - L2 \right) .
We read the roots as eigenvalues:
\color{red} \lambda_1 = L1 und \color{blue} \lambda_2 = L2.