Calculus, 10th Edition (Anton)

Published by Wiley
ISBN 10: 0-47064-772-8
ISBN 13: 978-0-47064-772-1

Chapter 6 - Exponential, Logarithmic, And Inverse Trigonometric Functions - 6.5 L'Hopital's Rule; Indeterminate Forms - Exercises Set 6.5 - Page 448: 38

Answer

$1$

Work Step by Step

Our aim is to evaluate the limit for $\lim\limits_{x \to 0^{+}} (e^{2x}-1)^x$ Let us consider that $y=(e^{2x}-1)^x \implies \ln y=x \ln (e^{2x}-1)=\dfrac{\ln (e^{2x}-1)}{1/x}$ But $\lim\limits_{x \to 0^{+}} \dfrac{\ln (e^{2x}-1)}{1/x}=\dfrac{\infty}{\infty}$ We can see that the numerator and denominator have a limit of $\infty$, so the limit shows the indeterminate form of type $\dfrac{\infty}{\infty}$. So, we will apply L-Hospital's rule which can be defined as: $\lim\limits_{x \to a} \dfrac{P(x) }{Q(x)}=\lim\limits_{x \to a}\dfrac{P'(x)}{Q'(x)}$ where, $a$ can be any real number, infinity or negative infinity. $\lim\limits_{x \to 0^{+}} \dfrac{\ln (e^{2x}-1)}{1/x} =\lim\limits_{x \to 0^{+}} \dfrac{-2x^2}{1-e^{-2x}} =\dfrac{\infty}{\infty}$ Again apply L-Hospital's rule to obtain: $\lim\limits_{x \to 0^{+}} \dfrac{-2x^2}{1-e^{-2x}} =\dfrac{-4x}{2e^{-2x}}=0$ Thus, we have: $\lim\limits_{x \to 0^{+}} y=e^0=1$
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