A <- matrix(c(1,3,2,4), nrow=2, ncol=2) \[\mathbf{A} = \left[\begin{array}
{rrr}
1 & 2 \\
3 & 4 \\
\end{array}\right]
\]
\[\mathbf{A} = \left[\begin{array}
{rrr}
1-\lambda & 2 \\
3 & 4-\lambda \\
\end{array}\right]
\]
\[
(1-\lambda)(4-\lambda)-6 = 0
\]
\[ (4-4\lambda-\lambda+\lambda^2-6) =0 \]
\[ Characteristics Equation = \lambda^2-5\lambda-2=0 \]