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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 10.2.19

In Exercises 15–22, determine if the geometric series converges or diverges. If a series converges, find its sum.
1 − (2/e) + (2/e)² − (2/e)³ + (2/e)⁴ − …

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1
Identify the first term \( a \) and the common ratio \( r \) of the geometric series. The series is \( 1 - \frac{2}{e} + \left(\frac{2}{e}\right)^2 - \left(\frac{2}{e}\right)^3 + \left(\frac{2}{e}\right)^4 - \cdots \), so \( a = 1 \) and \( r = -\frac{2}{e} \).
Recall that a geometric series \( \sum_{n=0}^\infty ar^n \) converges if and only if the absolute value of the common ratio is less than 1, i.e., \( |r| < 1 \).
Calculate \( |r| = \left| -\frac{2}{e} \right| = \frac{2}{e} \). Since \( e \approx 2.718 \), compare \( \frac{2}{e} \) to 1 to determine convergence.
If the series converges, use the formula for the sum of an infinite geometric series: \[ S = \frac{a}{1 - r} \]. Substitute the values of \( a \) and \( r \) into this formula.
Write the sum expression explicitly as \( S = \frac{1}{1 - \left(-\frac{2}{e}\right)} = \frac{1}{1 + \frac{2}{e}} \), which can be simplified further if needed.

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주요 개념

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

Geometric Series

A geometric series is a sum of terms where each term is found by multiplying the previous term by a constant ratio, r. It has the form a + ar + ar² + ar³ + ..., where a is the first term. Understanding this structure is essential to analyze the given series.
추천 영상:
가이드 코스
06:00
Geometric Series

Convergence Criteria for Geometric Series

A geometric series converges if the absolute value of the common ratio |r| is less than 1. If |r| ≥ 1, the series diverges. This criterion helps determine whether the infinite sum approaches a finite value.
추천 영상:
가이드 코스
06:00
Geometric Series

Sum of a Convergent Geometric Series

If a geometric series converges, its sum can be calculated using the formula S = a / (1 - r), where a is the first term and r is the common ratio. This formula provides a direct way to find the total sum of the infinite series.
추천 영상:
가이드 코스
06:00
Geometric Series