\(A=\sqrt{x-2\sqrt{x-1}}+\sqrt{x+2\sqrt{x-1}}\)
\(=\sqrt{x-1-2\sqrt{x-1}+1}+\sqrt{x-1+2\sqrt{x-1}+1}\)
\(=\sqrt{\left(\sqrt{x-1}-1\right)^2}+\sqrt{\left(\sqrt{x-1}+1\right)^2}\)
\(=\left|\sqrt{x-1}-1\right|+\left|\sqrt{x-1}+1\right|\)
\(=\left|1-\sqrt{x-1}\right|+\left|\sqrt{x-1}+1\right|\)
\(\ge\left|1-\sqrt{x-1}+\sqrt{x-1}+1\right|=2\)
Dấu "=" xảy ra \(\Leftrightarrow\left(1-\sqrt{x-1}\right)\left(\sqrt{x-1}+1\right)\ge0\Leftrightarrow0\le x\le2\)
Vậy \(A_{min}=2\) tại \(0\le x\le2\)
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vay a =2 0<x<2 nha bn
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