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Ch. 10 - Infinite Sequences and Series
Hass - Thomas' Calculus 15th Edition
Hass15th EditionThomas' CalculusISBN: 9780137616077당신이 사용하는 게 아니라요?교과서 변경
10장, 문제 10.2.64

Which series in Exercises 53–76 converge, and which diverge? Give reasons for your answers. If a series converges, find its sum.
∑ (from n = 1 to ∞) (1 − 1/n)ⁿ

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1
First, identify the general term of the series: \(a_n = \left(1 - \frac{1}{n}\right)^n\).
Next, analyze the behavior of the term \(a_n\) as \(n\) approaches infinity by finding the limit \(\lim_{n \to \infty} \left(1 - \frac{1}{n}\right)^n\).
Recall the known limit \(\lim_{n \to \infty} \left(1 - \frac{1}{n}\right)^n = e^{-1}\), which is a nonzero constant.
Since the terms \(a_n\) do not approach zero, apply the Divergence Test (also called the nth-term test for divergence), which states that if \(\lim_{n \to \infty} a_n \neq 0\), then the series \(\sum a_n\) diverges.
Conclude that the series \(\sum_{n=1}^\infty \left(1 - \frac{1}{n}\right)^n\) diverges because its terms do not tend to zero, so it does not converge and therefore does not have a finite sum.

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주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Convergence and Divergence of Infinite Series

An infinite series converges if the sequence of its partial sums approaches a finite limit; otherwise, it diverges. Determining convergence involves testing whether the terms decrease sufficiently fast and if the sum stabilizes as more terms are added.
추천 영상:
가이드 코스
06:52
Convergence of an Infinite Series

Limit of the General Term

A necessary condition for series convergence is that the general term approaches zero as n approaches infinity. If the limit of the term (1 - 1/n)^n is not zero, the series must diverge by the Test for Divergence.
추천 영상:
05:50
One-Sided Limits

Behavior of the Term (1 - 1/n)^n

The expression (1 - 1/n)^n approaches 1/e as n becomes large. Understanding this limit helps determine the behavior of the series terms and whether the series can converge or diverge.
추천 영상:
가이드 코스
05:44
Divergence Test (nth Term Test)