1: Thay x=16 vào A, ta được:
\(A=\dfrac{4+2}{4+1}=\dfrac{6}{5}\)
2: \(B=\dfrac{x+\sqrt{x}+14}{x-4}-\dfrac{5}{\sqrt{x}-2}\)
\(=\dfrac{x+\sqrt{x}+14}{\left(\sqrt{x}+2\right)\left(\sqrt{x}-2\right)}-\dfrac{5}{\sqrt{x}-2}\)
\(=\dfrac{x+\sqrt{x}+14-5\left(\sqrt{x}+2\right)}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}\)
\(=\dfrac{x+\sqrt{x}+14-5\sqrt{x}-10}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}=\dfrac{x-4\sqrt{x}+4}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}\)
\(=\dfrac{\left(\sqrt{x}-2\right)^2}{\left(\sqrt{x}-2\right)\left(\sqrt{x}+2\right)}=\dfrac{\sqrt{x}-2}{\sqrt{x}+2}\)
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