Math Problem Statement

Test the series for convergence or divergence: \(\frac{8}{9} - \frac{8}{11} + \frac{8}{13} - \frac{8}{15} + \frac{8}{17} - \dots\)

Solution

To analyze the convergence or divergence of this series, let's first rewrite it in a general form.

The series presented is: 89811+813815+817\frac{8}{9} - \frac{8}{11} + \frac{8}{13} - \frac{8}{15} + \frac{8}{17} - \cdots

From Step 1, we can observe that this is an alternating series, and it suggests a summation form: n=1(1)n182n+7\sum_{n=1}^{\infty} (-1)^{n-1} \frac{8}{2n+7}

Step-by-Step Analysis:

  1. Identify the Terms: The general term for the series is given as 82n+7\frac{8}{2n+7}.

  2. Alternating Series Test: To determine convergence, we can apply the Alternating Series Test (Leibniz's Test), which states that if a series has terms of the form (1)nan(-1)^{n} a_n and:

    • ana_n is positive,
    • ana_n is decreasing,
    • limnan=0\lim_{n \to \infty} a_n = 0, then the series converges.
  3. Apply the Conditions:

    • Positivity: The terms 82n+7\frac{8}{2n+7} are positive.
    • Decreasing: As nn increases, 2n+72n+7 grows, so 82n+7\frac{8}{2n+7} decreases.
    • Limit to Zero: limn82n+7=0\lim_{n \to \infty} \frac{8}{2n+7} = 0.

Since all three conditions are satisfied, the series converges by the Alternating Series Test.

Would you like further details or explanations on any specific part?

Here are some related questions for practice:

  1. How do you apply the Alternating Series Test for convergence?
  2. What are other tests for convergence, such as the Ratio Test or Root Test?
  3. How do you determine if a non-alternating series converges or diverges?
  4. What is the difference between absolute and conditional convergence?
  5. Can a series diverge even if its terms approach zero?

Tip: For alternating series, always verify if the terms decrease monotonically and approach zero to apply the Alternating Series Test effectively.

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Math Problem Analysis

Mathematical Concepts

Series
Alternating Series
Convergence and Divergence

Formulas

General form of the series: \(\sum_{n=1}^{\infty} (-1)^{n-1} \frac{8}{2n+7}\)

Theorems

Alternating Series Test (Leibniz's Test)

Suitable Grade Level

College