\[1)\ f(x) = \left\{ \begin{matrix} \log_{2}(x - 1)\ при\ x \leq 3 \\ (x - 5)^{2}\ \text{\ \ \ \ \ \ \ }при\ x > 3 \\ \end{matrix} \right.\ \]
\[Ответ:\ \ (1;\ 3) \cup (3;\ + \infty).\]
\[2)\ f(x) = \left\{ \begin{matrix} \sqrt{x + 3}\ \text{\ \ \ \ \ \ \ \ \ \ }при\ x > 3 \\ x + 3\ при - 3 \leq x \leq 3 \\ (x + 3)^{2}\text{\ \ \ }\ при\ x < - 3 \\ \end{matrix} \right.\ \]
\[Ответ:\ \ ( - \infty;\ 3) \cup (3;\ + \infty).\]