Solution
= Solution
{c}
The elimination in <2/c/i> determines $x_3$ uniquely exactly when $\lambda\ne5$. The other two coordinates are then also fixed. Explicitly,
$$
\boxed{\lambda\ne5:\quad
\mathbf x=\begin{pmatrix}
1-2(\mu-2)/(\lambda-5)\\
2-5(\mu-2)/(\lambda-5)\\
(\mu-2)/(\lambda-5)
\end{pmatrix}.}
$$
For $\lambda=5$, the reduced equation is either inconsistent or leaves $x_3$ free, so a unique solution is impossible.