15 Three planes have equations
$$\begin{aligned}
x + k y + 3 z & = 1
3 x + 4 y + 2 z & = 3
x + 3 y - z & = - k
\end{aligned}$$
where \(k\) is a constant.
- Show that the planes meet at a point except for one value of \(k\), which should be determined.
- Show that, when the planes do meet at a point, the \(y\)-coordinate of this point is independent of \(k\).