8.
$$\mathbf { A } = \left( \begin{array} { r r r }
3 & 1 & - 1
1 & 1 & 1
k & 3 & 6
\end{array} \right) \quad k \neq 0$$
- Find, in terms of \(k , \mathbf { A } ^ { - 1 }\)
- Determine, in simplest form in terms of \(k\), the coordinates of the point where the following planes intersect.
$$\begin{array} { r }
3 x + y - z = 3
x + y + z = 1
k x + 3 y + 6 z = 6
\end{array}$$