MCQ
The function $f:R - \left\{ 0 \right\} \to R,$ given by $f\left( x \right) = \frac{1}{x} - \frac{2}{{{e^{2x}} - 1}}$ can be made continuous at $x=0$  by defining $f\left( 0 \right)$ .
  • A
    $2$
  • B
    $-1$
  • C
    $0$
  • $1$

Answer

Correct option: D.
$1$
d
$f(0)=\mathop {\lim }\limits_{x \to 0^-} f(x)=\mathop {\lim }\limits_{x \to 0^+} f(x)=\lim _{x \rightarrow 0} f(x)$

$f(0)=\mathop {\lim }\limits_{x \to 0} f(x)=\mathop {\lim }\limits_{x \to 0} \left[\frac{1}{x}-\frac{2}{e^{2 x}-1}\right]$

$=\mathop {\lim }\limits_{x \to 0} \frac{e^{2 x}-1-2 x}{x\left(e^{2 x}-1\right)}$

$\mathop {\lim }\limits_{x \to 0}\frac{1+2 x+\frac{(2 x)^{2}}{21}+\ldots .-1-2 x}{x\left(1+2 x+\frac{(2 x)^{2}}{21}+\ldots .-1\right)}$

$\mathop {\lim }\limits_{x \to 0} \frac{\frac{4 x^{2}}{2 !}+\frac{8 x^{3}}{3 !}+\ldots .}{x^{2}\left(2+\frac{4 x}{2 !}+\frac{8 x^{2}}{3 !}+\ldots .\right)}$

$f(0)=\frac{\frac{4}{2 !}}{2}=\frac{4}{2 \times 2}$

$f(0)=1$

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