Let
For what value of a {\displaystyle a} is v → {\displaystyle {\vec {v}}} an eigenvector of A {\displaystyle A} ?
![{\displaystyle A=\left[{\begin{array}{cc}1&-1\\-3&a\end{array}}\right],\qquad {\vec {v}}=\left[{\begin{array}{c}1\\3\end{array}}\right].}](https://wiki.ubc.ca/api/rest_v1/media/math/render/svg/ee4a3e8821c04d36653b30c3c7d107e56f9a0fc1)
is 
an eigenvector of 
?
