GIven $A^2-3A+1$,
Eigen value $1: 1-3+4=2$,
Eigen value $2= 4+6+4=14$
We know $AX=\lambda X$
$A^2X=A \lambda X= \lambda^2X$
$A^2X-3AX=\lambda^2X-3 \lambda X $
$A^2X-3AX+4IX=A =\lambda^2X-3 \lambda X+4IX $
$(A^2-3A+4I)X=(\lambda^2-3 \lambda +4I)X $
Eigenvalue of the matrix $(A^2 - 3A +4I)$ is $( λ^2 - 3λ + 4)$ and the eigenvector is same as $A$ which is $x_1,x_2$.