$p(\lambda) = \lambda^2 - 6\lambda + 8$; eigenvalues are $2$ and $4$

$p(\lambda) = \lambda^2 - 6\lambda + 8$; eigenvalues are $2$ and $3$

$p(\lambda) = \lambda^2 + 6\lambda + 8$; eigenvalues are $-2$ and $-4$

$p(\lambda) = \lambda^2 - 6\lambda + 9$; eigenvalues are $3$ (double root)