Another hw question i'm having trouble with How would I go about doing it?
The same way you would with any other 3 x 3 square matrix. k is just some number...
$\displaystyle \displaystyle \left|\begin{matrix}a&b&c\\d&e&f\\g&h&j\end{matrix }\right| = a\left|\begin{matrix}e&f\\h&j\end{matrix}\right| - b\left|\begin{matrix}d&f\\g&j\end{matrix}\right| + c\left|\begin{matrix}d&e\\g&h\end{matrix}\right|$