\[y = \frac{\sqrt{x^{2} + 6x + 8}}{3x + 18}\]
\[x^{2} + 6x + 8 \geq 0\]
\[x_{1} + x_{2} = - 6;\ \ \ x_{1} \cdot x_{2} = 8\]
\[x_{1} = - 4;\ \ \ x + 2 = - 2\]
\[(x + 4)(x + 2) \geq 0.\]
\[3x + 18 > 0\]
\[3x > - 18\]
\[x > - 6.\]
\[Ответ:x \in ( - \infty; - 6) \cup ( - 6;4\rbrack \cup \lbrack - 2; + \infty).\]