MCQ
$\lim _{x \rightarrow \infty}(\sqrt{x+\sqrt{x+\sqrt{x}}}-\sqrt{x})$ is equal to
  • A
    $0$
  • $\frac{1}{2}$
  • C
    $\log 2$
  • D
    $e^4$

Answer

Correct option: B.
$\frac{1}{2}$
(B)
$\lim _{x \rightarrow \infty}(\sqrt{x+\sqrt{x+\sqrt{x}}}-\sqrt{x})$
$=\lim _{x \rightarrow \infty} \frac{x+\sqrt{x+\sqrt{x}}-x}{\sqrt{x+\sqrt{x+\sqrt{x}}}+\sqrt{x}}$
$=\lim _{x \rightarrow \infty} \frac{\sqrt{x+\sqrt{x}}}{\sqrt{x+\sqrt{x+\sqrt{x}}}+\sqrt{x}}$
$=\lim _{x \rightarrow \infty} \frac{\sqrt{1+x^{-1 / 2}}}{\sqrt{1+\sqrt{x^{-1}+x^{-3 / 2}}}+1}=\frac{1}{2}$

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