Show that the application
$$\begin{aligned}
j : & \mathbb { K } ^ { 3 } \longrightarrow \mathcal { M } _ { 0 } ( 2 , \mathbb { K } ) \\
\left( \begin{array} { l } x \\ y \\ z \end{array} \right) & \longmapsto \left( \begin{array} { c c } x & y + z \\ y - z & - x \end{array} \right)
\end{aligned}$$
is an isomorphism of $\mathbb { K }$-vector spaces.