Solution
= Solution
Take
$$
A=\begin{pmatrix}1&0\\0&0\end{pmatrix},
\qquad
B=\begin{pmatrix}0&1\\0&0\end{pmatrix}.
$$
Then $AB=B\ne0$ and $(AB)^2=0$, whereas $BA=0$. Hence their <minimal polynomials> are
$$
\boxed{m_{AB}(t)=t^2,\qquad m_{BA}(t)=t}.
$$