Tìm GTLN ,GTNN

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viethoang1999

Tự tìm ĐKXĐ nhé!
1)
a)
$A=\sqrt{-\left ( x-\dfrac{1}{2} \right )^2+1}\le 1$
b)
$B=\sqrt{(2x^2-(x+1))^2+9}\ge 3$
$C=\sqrt{(5x-2)^2}+\sqrt{(5x)^2}=|5x-2|+|5x|=|2-5x|+|5x|\ge |2-5x+5x|=2$
Dấu "=" xảy ra khi: $(2-5x)5x\ge 0$
\Leftrightarrow $0\le x\le \dfrac{2}{5}$
 
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