Bài 2:
\(a,ĐK:x>0;x\ne1\\ b,P=\dfrac{1}{\sqrt{x}\left(\sqrt{x}-1\right)}:\dfrac{1-\sqrt{x}}{\sqrt{x}}-\dfrac{1}{\sqrt{x}+1}\\ P=\dfrac{1}{\sqrt{x}\left(\sqrt{x}-1\right)}\cdot\dfrac{\sqrt{x}}{1-\sqrt{x}}-\dfrac{1}{\sqrt{x}+1}\\ P=\dfrac{-1}{\left(\sqrt{x}-1\right)^2}-\dfrac{1}{\sqrt{x}+1}=\dfrac{-\sqrt{x}-1-x+2\sqrt{x}-1}{\left(\sqrt{x}-1\right)^2\left(\sqrt{x}+1\right)}\\ P=\dfrac{-x+\sqrt{x}-2}{\left(\sqrt{x}-1\right)^2\left(\sqrt{x}+1\right)}\)
\(c.x=4\Leftrightarrow P=\dfrac{-4+2-2}{\left(2-1\right)^2\left(2+1\right)}=-\dfrac{4}{3}\)
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