a) Ta có: \(B=\left(\dfrac{8x\sqrt{x}-1}{2x-\sqrt{x}}-\dfrac{8x\sqrt{x}+1}{2x+\sqrt{x}}\right):\dfrac{2x+1}{2x-1}\)
\(=\left(\dfrac{\left(2\sqrt{x}-1\right)\left(4x+2\sqrt{x}+1\right)}{\sqrt{x}\left(2\sqrt{x}-1\right)}-\dfrac{\left(2\sqrt{x}+1\right)\left(4x-2\sqrt{x}+1\right)}{\sqrt{x}\left(2\sqrt{x}+1\right)}\right):\dfrac{2x+1}{2x-1}\)
\(=\dfrac{4x+2\sqrt{x}+1-4x+2\sqrt{x}-1}{\sqrt{x}}:\dfrac{2x+1}{2x-1}\)
\(=\dfrac{4\sqrt{x}}{\sqrt{x}}:\dfrac{2x+1}{2x-1}\)
\(=4\cdot\dfrac{2x-1}{2x+1}\)
\(=\dfrac{8x-4}{2x+1}\)
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