$\lim _{x \rightarrow 0} \frac{\left(1+\frac{x}{2}\right)^{5 / 7}-1}{x}=$

$\lim _{x \rightarrow 0} \frac{\left(1+\frac{x}{2}\right)^{5 / 7}-1}{x}=$
  1. $\frac{5}{7}$
  2. $\frac{10}{7}$
  3. $\frac{5}{14}$
  4. $\frac{5}{17}$

Solution

$\lim _{x \rightarrow 0} \frac{\left(1+\frac{x}{2}\right)^{5 / 7}-1}{x}$ Here, Limit is $\div$ form, so we can apply L-Hospital rule $ \begin{aligned} & =\lim _{x \rightarrow 0} \frac{\frac{5}{7}\left(1+\frac{x}{2}\right)^{-2 / 7} \cdot \frac{d}{d x}\left(\frac{x}{2}\right)-0}{1} \\ & =\lim _{x \rightarrow 0} \frac{5}{7}\left(1+\frac{x}{2}\right)^{-2 / 7} \cdot \frac{1}{2} \\ & =\frac{5}{7}(1+0)^{-2 / 7} \times \frac{1}{2}=\frac{5}{14} \end{aligned} $ Hence, option (3) is correct

Asked in: AP EAMCET 2020 (22 Sep Shift 2)

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