Đáp án:
$\displaystyle \begin{array}{{>{\displaystyle}l}} 46.3.B\\ 47.3.B\\ 48.3.A\\ 49.3.D\\ 50.3.A \end{array}$
Giải thích các bước giải:
$\displaystyle \begin{array}{{>{\displaystyle}l}} 46.3.\ \sqrt{-16a} -\sqrt{4a^{2} -4a+1} ,\ ĐKXĐ:\ a\leqslant 0\\ Thay\ a=\frac{-1}{4}( tm) \ vào\ ta\ được:\\ \sqrt{-16.\frac{-1}{4}} -\sqrt{4.\left(\frac{1}{4}\right)^{2} -4.\frac{-1}{4} +1} =\frac{1}{2} \Rightarrow B\\ 47.3.\ \sqrt{\frac{a}{b}} +\frac{a}{b} .\sqrt{\frac{b}{a}} =\sqrt{\frac{a}{b}} +\sqrt{\frac{a^{2} b}{b^{2} a}} =\sqrt{\frac{a}{b}} +\sqrt{\frac{a}{b}} =2\sqrt{\frac{a}{b}}\\ \Rightarrow B\\ 48.3.\ \frac{\sqrt{4a^{2} b^{4}}}{\sqrt{36a^{4} b^{4}}} =\frac{-2ab^{2}}{6a^{2} b^{2}}( \ vì\ a< 0\ và\ b\neq 0)\\ =\frac{-1}{3a} \Rightarrow A\\ 49.3.\ \sqrt[3]{x-2} +5=0\Leftrightarrow \sqrt[3]{x-2} =-5\\ \Leftrightarrow x-2=-125\Leftrightarrow x=-123\Rightarrow D\\ 50.3.\ E=\sqrt[3]{8} +\sqrt[3]{-27} -\sqrt{64} :\sqrt{4} =2-3-\frac{8}{2} =-5\Rightarrow A \end{array}$
