\[\begin{array}{l}
x,\,\,y,\,\,\,z\,\,la\,\,\,3\,\,so\,\,lien\,\,tiep\,\,cua\,\,CSC\\
\Rightarrow x + z = 2y\,\,\,\,\,\,\left( 1 \right)\\
Lai\,\,co:\,\,\left\{ \begin{array}{l}
yz = 12\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\left( 2 \right)\\
{x^2} = {y^2} + {z^2}\,\,\,\,\,\,\left( 3 \right)
\end{array} \right.\\
\Rightarrow \left( 2 \right) \Leftrightarrow y = \frac{{12}}{z}\\
\Rightarrow \left( 1 \right) \Leftrightarrow x + z = \frac{{24}}{z} \Leftrightarrow x = \frac{{24}}{z} - z\\
\Rightarrow \left( 3 \right) \Leftrightarrow {\left( {\frac{{24}}{z} - z} \right)^2} = \frac{{144}}{{{z^2}}} + {z^2}\\
\Leftrightarrow \frac{{576}}{{{z^2}}} - 48 + {z^2} = \frac{{144}}{{{z^2}}} + {z^2}\\
\Leftrightarrow \frac{{432}}{{{z^2}}} = 48\\
\Leftrightarrow {z^2} = 9\\
\Leftrightarrow \left[ \begin{array}{l}
z = 3\\
z = - 3
\end{array} \right. \Rightarrow \left[ \begin{array}{l}
\left\{ \begin{array}{l}
x = 5\\
y = 4\\
z = 3
\end{array} \right.\\
\left\{ \begin{array}{l}
x = - 5\\
y = - 4\\
z = - 3
\end{array} \right..
\end{array} \right.
\end{array}\]
