\[y^{2} + 6y = 0\]
\[y(y + 6) = 0\]
\[y_{1} = 0;\ \ \ y_{2} = - 6.\]
\[- x_{1}^{2} + 3 \cdot 0 = - 9\]
\[x_{1}^{2} = 9\]
\[x_{1} = \pm 3.\]
\[- x_{2}^{2} + 3 \cdot ( - 6) = - 9\]
\[- x_{2}^{2} = - 9 + 18 \Longrightarrow \varnothing\]
\[Ответ:( - 3;0);(3;0).\]