Solution (source code)

= Solution

The coefficient <matrix> has <determinant>
$$
\det\begin{pmatrix}2&1&0\\1&3&\mu\\0&1&2\end{pmatrix}=2(6-\mu)-2=10-2\mu.
$$
A homogeneous <linear system> has a nonzero solution exactly when this is a <singular matrix>. Therefore
$$
\boxed{\mu=5.}
$$
At this value all solutions are $(x,y,z)=t(1,-2,1)$, with $t\ne0$ for a nonzero solution.