\[x^{2} + 6x - 13 = 0\]
\[x_{1} + x_{2} = - 6;\ \ x_{1} \cdot x_{2} = - 13\]
\[x_{1}^{2} + x_{2}^{2} =\]
\[= x_{1}^{2} + 2x_{1}x_{2} + x_{2}^{2} - 2x_{1}x_{2} =\]
\[= \left( x_{1} + x_{2} \right)^{2} - 2x_{1}x_{2} =\]
\[= ( - 6)^{2} - 2 \cdot ( - 13) = 36 + 26 = 62.\]
\[Ответ:62.\]