$\displaystyle \begin{array}{{>{\displaystyle}l}} \sqrt{2x-1} xác\ định\ khi\ 2x-1\geqslant 0\ \rightarrow x\geqslant \frac{1}{2} \ \\ \sqrt{3x-2} \ xác\ định\ khi\ 3x-2\geqslant 0\ \rightarrow x\geqslant \frac{2}{3} \ \\ \sqrt{4-8x} \ xác\ định\ khi\ 4-8x\geqslant 0\ \rightarrow x\leqslant \frac{1}{2} \ \\ \frac{1}{\sqrt{2x+1}} \ xác\ định\ khi\ 2x+1 >0\ \rightarrow x >\frac{-1}{2}\\ \frac{5}{\sqrt{3x+5} \ } \ xác\ định\ khi\ 3x+5 >0\ \rightarrow x >\frac{-5}{3} \ \\ \frac{-3}{\sqrt{7x+8}} \ xác\ định\ khi\ 7x+8 >0\ \rightarrow x >\frac{-8}{7} \ \\ \frac{\sqrt{6x-2}}{-5} \ xác\ định\ khi\ 6x-2\geqslant 0\ \rightarrow x\geqslant \frac{1}{3} \ \\ Bài\ 2:\ \\ 1)\sqrt{22-8\sqrt{6}} =\sqrt{16-2.4\sqrt{6} +6}\\ =\sqrt{\left( 4-\sqrt{6}\right)^{2}} =|4-\sqrt{6} |\\ =4-\sqrt{6}\left( \ 4 >\sqrt{6}\right) \ \\ 2)\sqrt{16-6\sqrt{7}} =\sqrt{9-2.3\sqrt{7} +7} \ \\ \sqrt{\left( 3-\sqrt{7}\right)^{2}} =|3-\sqrt{7} |\\ =3-\sqrt{7}\left( 3 >\sqrt{7}\right) \ \\ 3)\sqrt{6+2\sqrt{5}} =\sqrt{1+2\sqrt{5} +5} \ \\ =\sqrt{\left( 1+\sqrt{5}\right)^{2}} =|1+\sqrt{5} |\\ =1+\sqrt{5} \ \\ 4\ trùng\ câu\ 2\ \\ 5)\sqrt{\frac{9}{4} -\sqrt{2}} \ =\sqrt{\frac{9-2.2\sqrt{2}}{4}}\\ =\sqrt{\frac{8-2.2\sqrt{2} +1}{4}} =\sqrt{\frac{\left( 2\sqrt{2} -1\right)^{2}}{4}} \ \\ =\frac{|2\sqrt{2} -1|}{2} =\frac{2\sqrt{2} -1}{2} \ \\ 6)\sqrt{\frac{129}{16} +\sqrt{2}} =\sqrt{\frac{129+2.8\sqrt{2}}{16}}\\ =\sqrt{\frac{128+2.8\sqrt{2} +1}{16}} =\sqrt{\frac{\left( 8\sqrt{2} +1\right)^{2}}{16}}\\ =\frac{8\sqrt{2} +1}{4} \ \\ 7)\sqrt{\left( 3-\sqrt{11}\right)^{2}} =|3-\sqrt{11} |\ \\ =\sqrt{11} -3\ \left(\sqrt{11} >3\right) \ \\ 8)\sqrt{\left(\sqrt{17} -4\right)^{2}} =|\sqrt{17} -4|\\ =\sqrt{17} -4\ \left( \ \sqrt{17} >4\right) \ \ \end{array}$