b) \(\dfrac{2}{5}\sqrt{25x-50}=6\)
Đk: \(x\ge2\)
Pt\(\Rightarrow\sqrt{25x-50}=15\Rightarrow25x-50=15^2\)
\(\Rightarrow25x=275\Rightarrow x=11\left(tmđk\right)\)
c) \(\dfrac{\sqrt{x}-1}{3}\cdot\left(\dfrac{\sqrt{x}+1}{\sqrt{x}-2}-\dfrac{\sqrt{x}+2}{\sqrt{x}-1}\right)\)
Đk: \(x\ge0\)
\(=\dfrac{\sqrt{x}-1}{3}\cdot\left(\dfrac{\left(\sqrt{x}+1\right)\left(\sqrt{x}-1\right)-\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}-1\right)}\right)\)
\(=\dfrac{x-1-\left(x-4\right)}{3\cdot\left(\sqrt{x}-2\right)}=\dfrac{3}{3\left(\sqrt{x}-2\right)}=\dfrac{1}{\sqrt{x}-2}\)
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