Question Bank • QB_EXP_EM_LIM_005 NAT • 2 Marks

Section 1: Engineering Mathematics

Calculus: Limits, Continuity & Differentiability

Subtopic: Indeterminate forms

Question Statement:

The value of the limit $L = \lim_{x \to \infty} \left(1 + \frac{6}{x}\right)^x$ for $k = 6$ is ________ (round off to two decimal places).

Answer Key:

403.43

Step-by-Step Solution & Explanation

This is an indeterminate form of type $1^\infty$. Taking natural logarithm of both sides: $\ln L = \lim_{x \to \infty} x \ln\left(1 + \frac{6}{x}\right) = \lim_{x \to \infty} \frac{\ln\left(1 + \frac{6}{x}\right)}{\frac{1}{x}}$ Applying L'Hospital's rule: $\ln L = \lim_{x \to \infty} \frac{\frac{1}{1 + k/x} \cdot \left(-\frac{k}{x^2}\right)}{-\frac{1}{x^2}} = \lim_{x \to \infty} \frac{6}{1 + k/x} = 6$ Exponentiating both sides: $L = e^{6} = 403.43$
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