Solution
= Solution
The <matrix> form is
$$
\boxed{\begin{pmatrix}1&2&3\\1&1&a-1\\a&2&3\end{pmatrix}
\begin{pmatrix}x\\y\\z\end{pmatrix}
=\begin{pmatrix}1\\2\\3\end{pmatrix}}.
$$
= Solution
The <matrix> form is
$$
\boxed{\begin{pmatrix}1&2&3\\1&1&a-1\\a&2&3\end{pmatrix}
\begin{pmatrix}x\\y\\z\end{pmatrix}
=\begin{pmatrix}1\\2\\3\end{pmatrix}}.
$$