tìm min

E

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$\dfrac{a}{2\sqrt{b}-5}+2\sqrt{b}-5 \ge 2\sqrt{a}$

$\dfrac{b}{2\sqrt{c}-5}+2\sqrt{c}-5 \ge 2\sqrt{b}$

$\dfrac{c}{2\sqrt{a}-5}+2\sqrt{a}-5 \ge 2\sqrt{c}$

\Rightarrow $A \ge 15$

Dấu "=" xảy ra khi và chỉ khi $a=b=c=25$

 
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