\[\boxed{\mathbf{1485}\mathbf{.}}\]
\[1)\ y = \sqrt{\frac{x - 3}{x + 3}}\]
\[\frac{x - 3}{x + 3} \geq 0\]
\[(x + 3)(x - 3) \geq 0\]
\[x < - 3\ и\ x \geq 3.\]
\[Ответ:\ \ x \in ( - \infty;\ - 3) \cup \lbrack 3;\ + \infty).\]
\[2)\ y = \sqrt{\log_{3}\frac{2x + 1}{x - 6}}\]
\[\frac{2x + 1}{x - 6} > 0\]
\[(2x + 1)(x - 6) > 0\]
\[x < - \frac{1}{2}\ и\ x > 6.\]
\[\log_{3}\frac{2x + 1}{x - 6} \geq 0\]
\[\log_{3}\frac{2x + 1}{x - 6} \geq \log_{3}3^{0}\]
\[\frac{2x + 1}{x - 6} \geq 1\ \ \ \ \ | \bullet (x - 6)^{2}\]
\[(2x + 1)(x - 6) \geq (x - 6)^{2}\]
\[(2x + 1)(x - 6) - (x - 6)^{2} \geq 0\]
\[(x - 6)\left( (2x + 1) - (x - 6) \right) \geq 0\]
\[(x - 6)(2x + 1 - x + 6) \geq 0\]
\[(x + 7)(x - 6) \geq 0\]
\[x \leq - 7\ и\ x > 6.\]
\(Ответ:\ \ x \in ( - \infty;\ - 7\rbrack \cup (6;\ + \infty).\)