2 câu trả lời
Đáp án:
`(\sqrt{8 - 2\sqrt{15}}) - (\sqrt{48 + 6\sqrt{15}})`
`= (\sqrt{(\sqrt{3})² - 2.\sqrt{3}.\sqrt{5} + (\sqrt{5})^2}) - (\sqrt{(3\sqrt{5})^2 +2. 3\sqrt{5}. \sqrt{3} + (\sqrt{3})^2})`
`= \sqrt{(\sqrt{3} - \sqrt{5})^2} - \sqrt{(3\sqrt{5} +\sqrt{3})^2}`
`= |\sqrt{3} - \sqrt{5}| - |3\sqrt{5} + \sqrt{3}|`
`= \sqrt{5} - \sqrt{3} - 3\sqrt{5} - \sqrt{3}`
`= -2\sqrt{5} - 2\sqrt{3}`
$\sqrt{8-2\sqrt{15}}$ - $\sqrt{48+6\sqrt{15}}$
`=` $\sqrt{( 5 - 2\sqrt{3}.\sqrt{5} + 3)}$ - $\sqrt{( 45 + 2.3\sqrt{5} + 3)}$
`=` $\sqrt{(\sqrt{5} - \sqrt{3})²}$ - $\sqrt{([3\sqrt{5})+\sqrt{3]²}}$
`=` |$\sqrt{5}$ - $\sqrt{3}$| - |3$\sqrt{5}$ + $\sqrt{3}$|
`=` $\sqrt{5}$ -$\sqrt{3}$- 3$\sqrt{5}$ - $\sqrt{3}$
`= -2`$\sqrt{5}$ `- 2`$\sqrt{3}$
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