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Ch. 7 - Transcendental Functions
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077Not the one you use?Change textbook
Chapter 7, Problem 7.PE.97

Use l’Hôpital’s Rule to find the limits in Exercises 85–108.
97. lim(x→0) (10^x - 1)/x

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Identify the limit expression: \(\lim_{x \to 0} \frac{10^x - 1}{x}\).
Check the form of the limit by substituting \(x = 0\): numerator becomes \(10^0 - 1 = 1 - 1 = 0\) and denominator is \(0\), so the limit is of the form \(\frac{0}{0}\), which is indeterminate and allows the use of l'Hôpital's Rule.
Apply l'Hôpital's Rule by differentiating the numerator and denominator separately with respect to \(x\): differentiate \$10^x\( using the chain rule, recalling that \(\frac{d}{dx} a^x = a^x \ln(a)\) for a positive constant \)a$.
Write the new limit after differentiation: \(\lim_{x \to 0} \frac{\frac{d}{dx}(10^x - 1)}{\frac{d}{dx} x} = \lim_{x \to 0} \frac{10^x \ln(10)}{1}\).
Evaluate the new limit by substituting \(x = 0\): \(10^0 \ln(10) = 1 \cdot \ln(10)\), which gives the value of the original limit.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Limits and Indeterminate Forms

Limits describe the behavior of a function as the input approaches a certain value. When direct substitution results in an indeterminate form like 0/0, special techniques such as l’Hôpital’s Rule are needed to evaluate the limit.
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l’Hôpital’s Rule

l’Hôpital’s Rule is a method for evaluating limits that yield indeterminate forms 0/0 or ∞/∞. It states that the limit of a ratio of functions can be found by taking the limit of the ratio of their derivatives, provided certain conditions are met.
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Derivative of Exponential Functions

The derivative of an exponential function a^x, where a > 0, is given by a^x times the natural logarithm of a (ln a). This rule is essential when applying l’Hôpital’s Rule to limits involving exponential expressions.
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