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Ch. 10 - Sequences and Infinite Series
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Non è quello che usi tu?Cambia libro di testo
Capitolo 10, Problema 10.8.69

11–86. Applying convergence tests Determine whether the following series converge. Justify your answers.


∑ (from k = 1 to ∞)(1 + 1 / (2k))ᵏ

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First, identify the general term of the series: \(a_k = \left(1 + \frac{1}{2k}\right)^k\).
To determine convergence, consider the behavior of \(a_k\) as \(k\) approaches infinity. Calculate the limit \(\lim_{k \to \infty} a_k = \lim_{k \to \infty} \left(1 + \frac{1}{2k}\right)^k\).
Recognize that this limit resembles the form of the exponential function \(e^x\), where \(\lim_{n \to \infty} \left(1 + \frac{x}{n}\right)^n = e^x\). Here, \(x = \frac{1}{2}\), so the limit becomes \(e^{1/2}\).
Since the limit of the terms \(a_k\) is \(e^{1/2}\), which is a positive number not equal to zero, apply the Divergence Test (also called the Test for Divergence), which states that if \(\lim_{k \to \infty} a_k \neq 0\), then the series \(\sum a_k\) diverges.
Conclude that because the terms do not approach zero, the series \(\sum_{k=1}^\infty \left(1 + \frac{1}{2k}\right)^k\) diverges.

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