Q. 29 In Exercises 21-30聽use one of t... [FREE SOLUTION]

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Chapter 7: Q. 29 (page 631)

In Exercises $21 - 30$ use one of the comparison tests to determine whether the series converges or diverges. Explain how the given series satisfies the hypotheses of the test you use.
role="math" localid="1649219965557" ${鈭�}_{k = 1}^{鈭�} \frac{1 + \ln k}{k^{3}}$ .

Short Answer

Expert verified

The series ${鈭�}_{k = 1}^{鈭�} \frac{1 + \ln k}{k^{3}}$ is convergent.

Step by step solution

Step 1. Given information

${鈭�}_{k = 1}^{鈭�} \frac{1 + \ln k}{k^{3}}$ .

Step 2. The limit comparison test states that for ∑k=1∞ ak and ∑k=1∞ bk be two series with positive terms then,

If $\lim_{k 鈫� 鈭�} \frac{a_{k}}{b_{k}} = L$ , where $L$ is any positive real number, then either both converge or both diverge.
If $\lim_{k 鈫� 鈭�} \frac{a_{k}}{b_{k}} = 0$ , and ${鈭�}_{k = 1}^{鈭�} b_{k}$ converges, then ${鈭�}_{k = 1}^{鈭�} a_{k}$ converges.
If $\lim_{k 鈫� 鈭�} \frac{a_{k}}{b_{k}} = 鈭�$ , and ${鈭�}_{k = 1}^{鈭�} b_{k}$ diverges, then ${鈭�}_{k = 1}^{鈭�} a_{k}$ diverges.

Step 3. The terms of the series ∑k=1∞ 1+ln kk3 are positive.

The expression $1 + \ln k$ satisfies the following inequality:

$1 + \ln k 鈮� k$ .

Find ${鈭�}_{k = 1}^{鈭�} b_{k}$ for the given series.

${鈭�}_{k = 1}^{鈭�} b_{k} = {鈭�}_{k = 1}^{鈭�} \frac{k}{k^{3}} = {鈭�}_{k = 1}^{鈭�} \frac{1}{k^{2}}$

Step 4. Next find limk→∞ akbk for the given series.

$\lim_{k 鈫� 鈭�} \frac{a_{k}}{b_{k}} = \lim_{k 鈫� 鈭�} \frac{\frac{1 + \ln k}{k^{3}}}{\frac{1}{k^{2}}} = \lim_{k 鈫� 鈭�} \frac{1 + \ln k}{k}$

$= 0$ [ using L'Hopital's rule]

Step 5. From the obtained values,

The value of $\lim_{k 鈫� 鈭�} \frac{a_{k}}{b_{k}} = 0$ which is a finite number.

The value of ${鈭�}_{k = 1}^{鈭�} b_{k} = {鈭�}_{k = 1}^{鈭�} \frac{1}{k^{2}}$ is convergent by $p -$ series test.

Therefore, the series ${鈭�}_{k = 1}^{鈭�} a_{k}$ is also convergent.

Hence, the given series is convergent.

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91影视

In Exercises $21 - 30$ use one of the comparison tests to determine whether the series converges or diverges. Explain how the given series satisfies the hypotheses of the test you use.
role="math" localid="1649219965557" ${鈭�}_{k = 1}^{鈭�} \frac{1 + \ln k}{k^{3}}$ .

Short Answer

Step by step solution

Step 1. Given information

Step 2. The limit comparison test states that for ∑k=1∞ ak and ∑k=1∞ bk be two series with positive terms then,

Step 3. The terms of the series ∑k=1∞ 1+ln kk3 are positive.

Step 4. Next find limk→∞ akbk for the given series.

Step 5. From the obtained values,

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91影视

In Exercises 21-30use one of the comparison tests to determine whether the series converges or diverges. Explain how the given series satisfies the hypotheses of the test you use.role="math" localid="1649219965557" 鈭�k=1鈭�1+lnkk3.

Short Answer

Step by step solution

Step 1. Given information

Step 2. The limit comparison test states that for ∑k=1∞ ak and ∑k=1∞ bk be two series with positive terms then,

Step 3. The terms of the series ∑k=1∞ 1+ln kk3 are positive.

Step 4. Next find limk→∞ akbk for the given series.

Step 5. From the obtained values,

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Math Textbooks

Statistics

Geometry

Logic and Functions

Decision Maths

Discrete Mathematics

Probability and Statistics

Study anywhere. Anytime. Across all devices.

In Exercises $21 - 30$ use one of the comparison tests to determine whether the series converges or diverges. Explain how the given series satisfies the hypotheses of the test you use.
role="math" localid="1649219965557" ${鈭�}_{k = 1}^{鈭�} \frac{1 + \ln k}{k^{3}}$ .