\(\sqrt {3 - x} + \sqrt {x - 5} \ge - 10\)
ĐK: \(\left\{{}\begin{matrix}3-x\ge0\\x-5\ge0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x\le3\\x\ge5\end{matrix}\right.\)
Do \(\sqrt{3-x}+\sqrt{x-5}\ge0\forall x\in\left[3;5\right]\)
\(\Rightarrow\sqrt{3-x}+\sqrt{x-5}\ge-10\\ \Rightarrow S=\left[3;5\right]\)