Chapter 9: Problem 4
For each given \(p\) -series, identify \(p\) and determine whether the series converges. $$\text { (a) } \sum_{k=1}^{\infty} k^{-4 / 3}$$ $$\text { (b) } \sum_{k=1}^{\infty} \frac{1}{\sqrt[4]{k}}$$ $$\text { (c) } \sum_{k=1}^{\infty} \frac{1}{\sqrt[3]{k^{5}}}$$ $$\text { (d) } \sum_{k=1}^{\infty} \frac{1}{k^{\pi}}$$
Short Answer
Step by step solution
Identify p-value in Series (a)
Determine Convergence for Series (a)
Identify p-value in Series (b)
Determine Convergence for Series (b)
Identify p-value in Series (c)
Determine Convergence for Series (c)
Identify p-value in Series (d)
Determine Convergence for Series (d)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Power Series
Though power series themselves utilize coefficients and variables, when dealing with p-series, we specifically focus on terms like \( k^{-p} \), where there is a constant exponent.Understanding how power series function is essential because they underpin many mathematical techniques. They can converge, meaning sum to a finite number, or diverge, implying they don't resolve to a usable number. This behavior depends on their characteristics.
P-Series Test
According to the p-series test:
- The series converges if \( p > 1 \).
- The series diverges if \( p \leq 1 \).
This straightforward rule simplifies analysis and helps solve series-related problems by providing neat conditions for evaluation.
Convergence and Divergence
In the context of p-series:
- Convergent series when \( p > 1 \) indicate a balance in terms' magnitude that diminishes to negligible values.
- Divergent series when \( p \leq 1 \) means the added terms remain significant enough to prevent restricting to a stable sum.
Exponent Identification
Let's look at an example:
- For \( \sum_{k=1}^{\infty} \frac{1}{\sqrt{4}{k}} \), rewrite this as \( k^{-1/4} \). Therefore \( p = \frac{1}{4} \).
- By contrast, the series \( \sum_{k=1}^{\infty} \frac{1}{k^{\pi}} \) clearly identifies \( p = \pi \).