Let $f : V \to V$ be a linear operator on a two-dimensional vector space $V$ over $\mathbb{K}$. Suppose that $f \neq \lambda\cdot \textrm{Id}$. Does there exist a vector $v$ such that $\{v, f(v)\}$ is a basis for $V$? Which is the matrix of $f$ with respect to the previous basis?
I showed the first claim, but which is the associated matrix? I think it is
$$ \left[\begin{matrix}0 & a_{12} \\ 1 & a_{22}\end{matrix}\right] $$ where $a_{22} \neq 0$. Is it correct or there is other to say?