Mathematics

Mathematics

Problem

Determine the value of lim⁡x→0(1+5x)1x\displaystyle \lim_{x\to 0}(1+5x)^{\tfrac{1}{x}}. a) e1/5e^{1/5} b) e5e^{5} c) 55 d) The limit does not exist.
Intuitive explanation

This limit has the indeterminate form 1∞1^{\infty}, which signals an exponential growth problem. The key insight is to use logarithms: take ln⁡\ln of the expression, find that limit first, then exponentiate back. You'll recognize the result as a close cousin of the famous limit lim⁡u→0(1+u)1/u=e\lim_{u\to 0}(1+u)^{1/u} = e.

Intuitive explanation

This limit has the indeterminate form 1∞1^{\infty}, which signals an exponential growth problem. The key insight is to use logarithms: take ln⁡\ln of the expression, find that limit first, then exponentiate back. You'll recognize the result as a close cousin of the famous limit lim⁡u→0(1+u)1/u=e\lim_{u\to 0}(1+u)^{1/u} = e.

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