a) \(P=\left(\dfrac{\sqrt{x}}{\sqrt{x}-2}-\dfrac{4}{x-2\sqrt{x}}\right):\dfrac{\sqrt{x}+2}{2}\)
\(P=\left[\dfrac{\sqrt{x}\cdot\sqrt{x}}{\sqrt{x}\left(\sqrt{x}-2\right)}-\dfrac{4}{\sqrt{x}\left(\sqrt{x}-2\right)}\right]\cdot\dfrac{2}{\sqrt{x}+2}\)
\(P=\dfrac{x-4}{\sqrt{x}\left(\sqrt{x}-2\right)}\cdot\dfrac{2}{\sqrt{x}+2}\)
\(P=\dfrac{\sqrt{x}+2}{\sqrt{x}}\cdot\dfrac{2}{\sqrt{x}+2}\)
\(P=\dfrac{2}{\sqrt{x}}\)
b) \(P\ge1\) khi
\(\Leftrightarrow\dfrac{2}{\sqrt{x}}\ge1\)
\(\Leftrightarrow\sqrt{x}\le2\)
\(\Leftrightarrow x\le4\)
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