\[x^{2} - 6x - 3 = 0\]
\[D_{1} = 9 + 3 = 12\]
\[x_{1,2} = 3 \pm \sqrt{12} = 3 \pm 2\sqrt{3}.\]
\[Ответ:x = 3 \pm 2\sqrt{3}.\]