Rút gọn : a) √32-3√50+2√8 b)( √7- √5) ² + √140 10/07/2021 Bởi Alaia 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) $-7\sqrt{2}$.}$ $\text{b) 12.}$ Bình luận
`a, \sqrt{32} – 3\sqrt{50} + 2\sqrt{8}` `= 4\sqrt{2} – 15\sqrt{2} + 4\sqrt{2}` `= -7\sqrt{2}` `b, (\sqrt{7}-\sqrt{5})^2 + \sqrt{140}` `= (\sqrt{7}-\sqrt{5})^2 + 2\sqrt{35}` `= 12 – 2\sqrt{35} + 2\sqrt{35}` `= 12` Bình luận
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) $-7\sqrt{2}$.}$
$\text{b) 12.}$
`a, \sqrt{32} – 3\sqrt{50} + 2\sqrt{8}`
`= 4\sqrt{2} – 15\sqrt{2} + 4\sqrt{2}`
`= -7\sqrt{2}`
`b, (\sqrt{7}-\sqrt{5})^2 + \sqrt{140}`
`= (\sqrt{7}-\sqrt{5})^2 + 2\sqrt{35}`
`= 12 – 2\sqrt{35} + 2\sqrt{35}`
`= 12`