Rút gọn : a) √32-3√50+2√8 b)( √7- √5) ² + √140

Hướng dẫn trả lời:

$\text{a) $\sqrt{32}$ – $3\sqrt{50}$ + $2\sqrt{8}$.}$

$\text{= $4\sqrt{2}$ – $15\sqrt{2}$ + $4\sqrt{2}$.}$

$\text{= $-7\sqrt{2}$.}$

$\text{b) $(\sqrt{7} – \sqrt{5})^2$ + $\sqrt{140}$.}$

$\text{= (7 – 2$\sqrt{35}$ + 5) + $2\sqrt{35}$.}$

$\text{= (12 – 2$\sqrt{35}$) + $2\sqrt{35}$.}$

$\text{= 12 – 2$\sqrt{35}$ + $2\sqrt{35}$.}$

$\text{= 12.}$

Đáp án:

$\text{a) $-7\sqrt{2}$.}$

$\text{b) 12.}$