Math Problem Statement

Evaluate the limit as x approaches 0 of (x * 5^x) / (5^x - 1).

Solution

To evaluate the limit:

limx0x5x5x1\lim_{{x \to 0}} \frac{x \cdot 5^x}{5^x - 1}

we can approach it by analyzing the behavior of both the numerator and the denominator as x0x \to 0.

  1. Expanding 5x5^x near x=0x = 0 using Taylor Series: For xx close to 0, we can approximate 5x5^x by its Taylor expansion: 5x1+xln(5)+x2(ln(5))22+5^x \approx 1 + x \ln(5) + \frac{x^2 (\ln(5))^2}{2} + \dots So, 5x1xln(5)5^x - 1 \approx x \ln(5)

  2. Rewrite the Limit: Substitute this approximation in the limit: limx0x5xxln(5)=limx0xx5xln(5)\lim_{{x \to 0}} \frac{x \cdot 5^x}{x \ln(5)} = \lim_{{x \to 0}} \frac{x}{x} \cdot \frac{5^x}{\ln(5)}

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Math Problem Analysis

Mathematical Concepts

Limits
Exponential Functions
Taylor Series Approximation

Formulas

Taylor series expansion for exponential functions near zero
lim(x→0) of f(x)/g(x) when both f(x) and g(x) approach 0

Theorems

L'Hôpital's Rule
Taylor Series Expansion

Suitable Grade Level

Grades 11-12 or College Calculus