b: \(=\dfrac{x-5\sqrt{x}+2x+10\sqrt{x}-3x-2}{x-25}\cdot\dfrac{2\left(\sqrt{x}-5\right)}{2\left(5\sqrt{x}-2\right)}\)
\(=\dfrac{5\sqrt{x}-2}{x-25}\cdot\dfrac{\sqrt{x}-5}{5\sqrt{x}-2}=\dfrac{1}{\sqrt{x}+5}\)
c: \(=\dfrac{-\sqrt{x}-6-\left(x-1\right)\left(\sqrt{x}-2\right)+x\left(\sqrt{x}+2\right)}{x-4}:\dfrac{\sqrt{x}+2-\sqrt{x}+2}{\sqrt{x}-2}\)
\(=\dfrac{-\sqrt{x}-6-x\sqrt{x}+2x+\sqrt{x}-2+x\sqrt{x}+2x}{x-4}\cdot\dfrac{\sqrt{x}-2}{4}\)
\(=\dfrac{4x-8}{\sqrt{x}+2}\cdot\dfrac{1}{4}=\dfrac{x-2}{\sqrt{x}+2}\)
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