Solution
= Solution
At $a=2$, eliminate the first column by $R_2\leftarrow R_2-2R_1$ and $R_3\leftarrow R_3-2R_1$ in the augmented <matrix>. The last two rows give $-z=-2$ and $-y+z=-1$. Hence $z=2$, $y=3$, and the first row then gives $x=-2$. Thus
$$
\boxed{(x,y,z)=(-2,3,2)}.
$$
The coefficient <determinant> at this parameter is nonzero, so this solution is unique.