Limits And Continuity — Medium JEE math MCQ
The value of $\lim_{x \to 0} \frac{e^x - 1 - x}{x^2}$ is:
- A. $0$
- B. $\frac{1}{2}$
- C. $1$
- D. $2$
Solution
As $x \to 0$, we get $\frac{0}{0}$ form.
**Method 1: L'Hôpital's Rule**
$$\lim_{x \to 0} \frac{e^x - 1 - x}{x^2} = \lim_{x \to 0} \frac{e^x - 1}{2x}$$ (still $\frac{0}{0}$)
$$= \lim_{x \to 0} \frac{e^x}{2} = \frac{1}{2}$$
**Method 2: Taylor Series**
$e^x = 1 + x + \frac{x^2}{2!} + \frac{x^3}{3!} + \ldots$
$e^x - 1 - x = \frac{x^2}{2} + \frac{x^3}{6} + \ldots$
$$\lim_{x \to 0} \frac{e^x - 1 - x}{x^2} = \lim_{x \to 0} \frac{\frac{x^2}{2} + \frac{x^3}{6} + \ldots}{x^2} = \frac{1}{2}$$
