If
\[
\vec a=2\hat i+3\mu\hat j-\hat k,
\qquad
\vec b=\mu\hat i-2\hat j+3\hat k,
\qquad
\vec c=\hat i+3\hat j-2\mu\hat k
\]
are three vectors such that
\[
\alpha\vec a+\beta\vec b+\gamma\vec c=\vec 0
\]
only when
\[
\alpha=\beta=\gamma=0,
\]
then the set of all real values of \(\mu\) is