Chapter 9: Problem 19
Does the series converge or diverge? $$\sum_{n=1}^{\infty} \frac{3}{(2 n-1)^{2}}$$
Short Answer
Expert verified
The series converges because it's a p-series with p > 1.
Step by step solution
01
Identify the Series Type
The given series is \( \sum_{n=1}^{\infty} \frac{3}{(2n-1)^2} \). Notice that it resembles a p-series because it is in the form \( \sum \frac{1}{n^p} \). Here, the general term is \( \frac{3}{(2n-1)^2} \).
02
Rewriting the Series
Rewrite the series to closely examine its behavior by factoring out the constant:\[\sum_{n=1}^{\infty} \frac{3}{(2n-1)^2} = 3 \sum_{n=1}^{\infty} \frac{1}{(2n-1)^2}.\]
03
Recognize the P-series
The series \( \sum_{n=1}^{\infty} \frac{1}{(2n-1)^2} \) is a p-series, where the general form is \( \sum \frac{1}{k^p} \) with \( k = 2n - 1 \) and \( p=2 \).
04
Apply the P-series Test
In a p-series \( \sum \frac{1}{k^p} \), it converges if \( p > 1 \). Here \( p = 2 \), which is greater than 1, indicating convergence.
05
Conclusion on Convergence
Since \( \sum_{n=1}^{\infty} \frac{1}{(2n-1)^2} \) converges by the p-series test, the original series \( \sum_{n=1}^{\infty} \frac{3}{(2n-1)^2} \) also converges, because a constant multiple of a convergent series is also convergent.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Convergent Series
A convergent series is a sequence of numbers where the sum approaches a specific finite value as more terms are added. This means that as you keep calculating the sum by adding more terms, the result becomes closer to a particular number. A classic example is the harmonic series, which converges if the sequence's terms decrease rapidly enough. For a series to be labeled as convergent:
- The sequence of partial sums must approach a finite limit.
- The terms of the series must get smaller as you progress through the series.
P-series Test
The p-series test is a common and useful tool to determine the convergence or divergence of series in the form \( \sum \frac{1}{n^p} \). It's an essential part of understanding series convergence:
- A p-series converges when \( p > 1 \).
- A p-series diverges when \( p \leq 1 \).
Series Convergence
Series convergence is about determining whether adding up all the terms in a series will settle on a specific value or not. A series converges when the infinite addition of terms results in a finite limit. This concept is pivotal in calculus and analysis:
- To determine convergence, apply tests such as the p-series test, ratio test, or comparison test.
- Each test has specific conditions and applications for when it is most useful.