For the matrix A=(1302)A = \begin{pmatrix} 1 & 3 \\ 0 & 2 \end{pmatrix}A=(1032), the characteristic polynomial χ(λ)=det(λI−A)\chi(\lambda) = \det(\lambda I - A)χ(λ)=det(λI−A) is:
λ2−3λ+2\lambda^2 - 3\lambda + 2λ2−3λ+2
λ2−3λ−2\lambda^2 - 3\lambda - 2λ2−3λ−2
λ2+3λ+2\lambda^2 + 3\lambda + 2λ2+3λ+2
λ2−2λ−3\lambda^2 - 2\lambda - 3λ2−2λ−3