\(1,\\ a,ĐK:x+2\ge0\Leftrightarrow x\ge-2\\ b,ĐK:\dfrac{x-6}{5}\ge0\Leftrightarrow x-6\ge0\left(5>0\right)\\ \Leftrightarrow x\ge6\\ 2,\\ a,=3\sqrt{5}+30\sqrt{5}-56\sqrt{5}=-23\sqrt{5}\\ b,=\sqrt{3}+2+\sqrt{3}+1=2\sqrt{3}+3\\ c,=2\sqrt{5}-16-\left(36-2\sqrt{5}\right)=4\sqrt{5}-52\\ d,=\sqrt{\left(3-\sqrt{2}\right)^2}+\sqrt{\left(3+\sqrt{2}\right)^2}\\ =3-\sqrt{2}+3+\sqrt{2}=6\)
\(3,\\ ĐK:-3x\ge0\Leftrightarrow x\le0\\ \sqrt{-3x}< 12\Leftrightarrow-3x< 144\\ \Leftrightarrow x< -48\left(tm\right)\)