\[y = \frac{\sqrt{x^{2} - 4x - 12}}{2x - 18}\]
\[x^{2} - 4x - 12 \geq 0\]
\[x_{1} + x_{2} = 4;\ \ \ x_{1} \cdot x_{2} = - 12\]
\[x_{1} = 6;\ \ \ x_{2} = - 2\]
\[(x + 2)(x - 6) \geq 0.\]
\[2x - 18 > 0\]
\[2x > 18\]
\[x > 9.\]
\[Ответ:x \in ( - \infty; - 2\rbrack \cup \lbrack 6;9) \cup (9; + \infty).\]