[Toán 9] Rút gọn biểu thức chứa căn

H

hoangtubongdem5

X

xuanquynh97

Ta có :
$\dfrac{7}{12}\sqrt{\dfrac{1}{12}}=\sqrt{\dfrac{49}{48}}$
$=\sqrt{1+\dfrac{1}{48}}$
$\dfrac{9}{4}\sqrt{\dfrac{1}{5}}=\sqrt{\dfrac{81}{80}}$
=$\sqrt{1+\dfrac{1}{80}}$
Do $\dfrac{1}{48} > \dfrac{1}{80}$
\Rightarrow $\dfrac{7}{12}\sqrt{\dfrac{1}{12}} > \dfrac{9}{4}\sqrt{\dfrac{1}{5}}$
 
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