Đáp án: $6)B$
$7)B$
$8)A$
$9)B$
$10)C$
Giải thích các bước giải:
$6)\sqrt{18.48}=\sqrt{9.2.16.3}=\sqrt{144.6}=\sqrt{144}.\sqrt{6}=12\sqrt{6}$
$7)\sqrt{2}.\sqrt{8}=\sqrt{2.8}=\sqrt{16}=4$
$8)\sqrt{(\sqrt{7}-2)^2}=|\sqrt{7}-2|=\sqrt{7}-2$
$9)\sqrt{(3-\sqrt{7})^2}=|3-\sqrt{7}|=3-\sqrt{7}$
$10)4\sqrt{3}=\sqrt{16.3}=\sqrt{48}$
`\frac{\sqrt{6}}{3}=\sqrt{\frac{6}{9}}=\sqrt{\frac{2}{3}}`
$-3\sqrt{2}=-\sqrt{9.2}=-\sqrt{18}$
$-2\sqrt{3}=-\sqrt{4.3}=-\sqrt{12}$
$\text{⇒C sai.}$
