Đáp án:
$-\sqrt{10}+5\sqrt{2}$
Hướng dẫn giải:
$\left(\sqrt{8}\:-3\sqrt{2}+\sqrt{10}\:\right)\:\left(\sqrt{20}-\sqrt{5}\right)$
$=\left(-\sqrt{2}+\sqrt{10}\right)\left(\sqrt{20}-\sqrt{5}\right)$
$=\left(-\sqrt{2}+\sqrt{10}\right)\sqrt{5}$
$=\sqrt{5}\left(-\sqrt{2}+\sqrt{10}\right)$
$=\sqrt{5}\left(-\sqrt{2}\right)+\sqrt{5}\sqrt{10}$
$=-\sqrt{5}\sqrt{2}+\sqrt{5}\sqrt{10}$
$=-\sqrt{10}+5\sqrt{2}$
