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Ch. 10 - Infinite Sequences and Series
Hass - Thomas' Calculus 15th Edition
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10장, 문제 10.7.28c

Intervals of Convergence
In Exercises 1–36, for what values of x does the series converge (c) conditionally?
∑ (from n = 0 to ∞) [ (−2)ⁿ (n + 1) (x − 1)ⁿ ]

검증된 단계별 안내
1
Identify the given power series: \(\sum_{n=0}^{\infty} (-2)^n (n+1) (x-1)^n\).
Rewrite the series in a form that isolates the variable term: \(\sum_{n=0}^{\infty} (n+1) \left[-2(x-1)\right]^n\).
Use the Root Test or Ratio Test to find the radius of convergence. For the Ratio Test, consider the limit \(L = \lim_{n \to \infty} \left| \frac{a_{n+1}}{a_n} \right|\), where \(a_n = (n+1) \left[-2(x-1)\right]^n\).
Solve the inequality \(L < 1\) to find the interval of convergence in terms of \(x\).
Check the endpoints of the interval separately by substituting them back into the original series to determine if the series converges absolutely, conditionally, or diverges at those points.

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주요 개념

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Radius and Interval of Convergence

The radius of convergence determines the distance from the center point within which a power series converges absolutely. The interval of convergence includes all x-values for which the series converges, possibly including endpoints where convergence must be tested separately.
추천 영상:
07:36
Radius of Convergence

Absolute vs. Conditional Convergence

A series converges absolutely if the series of absolute values converges; otherwise, it may converge conditionally if the original series converges but not absolutely. Conditional convergence often occurs at the endpoints of the interval of convergence.
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가이드 코스
07:51
Choosing a Convergence Test

Ratio Test for Convergence

The ratio test uses the limit of the absolute value of the ratio of consecutive terms to determine convergence. If this limit is less than one, the series converges absolutely; if greater than one, it diverges; if equal to one, the test is inconclusive and further analysis is needed.
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