\[x² + 12x + 6 = 0\]
\[x_{1} + x_{2} = - 12;\ \ x_{1} \cdot x_{2} = 6\]
\[x_{1}^{2} + x_{2}^{2} = \left( x_{1} + x_{2} \right)^{2} - 2x_{1}x_{2} =\]
\[= ( - 12)^{2} - 2 \cdot 6 = 144 - 12 = 132.\]
\[Ответ:132.\]