If the function given by $f(x)=\left(\frac{4 x+1}{1-4 x}\right)^{\frac{1}{x}}$ for $x \neq o$ is continuous…

If the function given by $f(x)=\left(\frac{4 x+1}{1-4 x}\right)^{\frac{1}{x}}$ for $x \neq o$ is continuous at $x=0$, then the value of $\mathrm{f}(\mathrm{o})$ is
  1. $\mathrm{e}^{8}$
  2. $\mathrm{e}^{10}$
  3. $\mathrm{e}^{-8}$
  4. $\mathrm{e}^{-10}$

Solution

$\begin{aligned} \lim _{x \rightarrow 0}\left(\frac{1+4 x}{1-4 x}\right)^{\frac{1}{x}} &=\frac{\lim _{x \rightarrow 0}(1+4 x)^{\frac{1}{x}}}{\lim _{x \rightarrow 0}(1-4 x)^{\frac{1}{x}}}=\frac{\left[\lim _{x \rightarrow 0}(1+4 x)^{\frac{1}{4 x}}\right]^{4}}{\left[\lim _{x \rightarrow 0}(1-4 x)^{\frac{-1}{4 x}}\right]^{-4}}=\frac{e^{4}}{e^{-4}} \\ &=e^{8} \end{aligned}$

Asked in: MHT CET 2020 (15 Oct Shift 2)

Practice more Continuity and Differentiability questions on Aicharya