\[6x² - 18 = 0\ \ \ | \cdot 6\]
\[x^{2} - 3 = 0\]
\[\left( x - \sqrt{3} \right)\left( x + \sqrt{3} \right) = 0\]
\[x - \sqrt{3} = 0,\ \ x + \sqrt{3} = 0\]
\[x = \sqrt{3}\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x = - \sqrt{3}\]
\[Ответ:x = \sqrt{3};\ x = - \sqrt{3}.\]