Q. 34 Use the ratio test for absolute ... [FREE SOLUTION]

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Chapter 7: Q. 34 (page 653)

Use the ratio test for absolute convergence to determine whether the series in Exercises 30鈥�35 converge absolutely or diverge.
${鈭�}_{k = 0}^{鈭�} \frac{{(- 2)}^{k} 1.3.5 . . . (2 k + 1)}{1.4.7 . . . (3 k + 1)}$

Short Answer

Expert verified

The series ${鈭�}_{k = 0}^{鈭�} \frac{{(- 2)}^{k} 1.3.5 . . . (2 k + 1)}{1.4.7 . . . (3 k + 1)}$ diverges.

Step by step solution

Step 1. Given Information.

The series:

${鈭�}_{k = 0}^{鈭�} \frac{{(- 2)}^{k} 1.3.5 . . . (2 k + 1)}{1.4.7 . . . (3 k + 1)}$

Step 2. Rewrite the series.

$a_{k} = \frac{{(- 2)}^{k} 1.3.5 . . . (2 k + 1)}{1.4.7 . . . (3 k + 1)}$

Step 3. Find ak+1

$a_{k + 1} = \frac{{(- 2)}^{k + 1} 1.3.5 . . . (2 (k + 1) + 1)}{1.4.7 . . . (3 (k + 1) + 1)} = \frac{{(- 2)}^{k + 1} 1.3.5 . . . (2 k + 3)}{1.4.7 . . . (3 k + 4)}$

Step 4. Calculate ak+1ak.

$|\frac{a_{k + 1}}{a_{k}}| = |\frac{\frac{{(- 2)}^{k + 1} 1.3.5 . . . (2 k + 3)}{1.4.7 . . . (3 k + 4)}}{\frac{{(- 2)}^{k} 1.3.5 . . . (2 k + 1)}{1.4.7 . . . (3 k + 1)}}| = |\frac{\frac{{(- 2)}^{k + 1} 1.3.5 . . . (2 k + 1) (2 k + 3)}{1.4.7 . . . (3 k + 1) (3 k + 4)}}{\frac{{(- 2)}^{k} 1.3.5 . . . (2 k + 1)}{1.4.7 . . . (3 k + 1)}}| = |\frac{- 2 (2 k + 3)}{3 k + 4}| = \frac{2 (2 k + 3)}{3 k + 4}$

Step 5. Take limits.

$\underset{k 鈫� 鈭�}{l i m} |\frac{a_{k + 1}}{a_{k}}| = \underset{k 鈫� 鈭�}{l i m} (\frac{2 (2 k + 3)}{3 k + 4}) = 2 \underset{k 鈫� 鈭�}{l i m} (\frac{k (2 + \frac{3}{k})}{k (3 + \frac{4}{k})}) = 2 (\frac{2}{3}) = \frac{4}{3} > 1$

So by the ratio test, the series diverges.

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91影视

Use the ratio test for absolute convergence to determine whether the series in Exercises 30鈥�35 converge absolutely or diverge.
${鈭�}_{k = 0}^{鈭�} \frac{{(- 2)}^{k} 1.3.5 . . . (2 k + 1)}{1.4.7 . . . (3 k + 1)}$

Short Answer

Step by step solution

Step 1. Given Information.

Step 2. Rewrite the series.

Step 3. Find ak+1

Step 4. Calculate ak+1ak.

Step 5. Take limits.

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91影视

Use the ratio test for absolute convergence to determine whether the series in Exercises 30鈥�35 converge absolutely or diverge.鈭�k=0鈭�(-2)k1.3.5...(2k+1)1.4.7...(3k+1)

Short Answer

Step by step solution

Step 1. Given Information.

Step 2. Rewrite the series.

Step 3. Find ak+1

Step 4. Calculate ak+1ak.

Step 5. Take limits.

One App. One Place for Learning.

Most popular questions from this chapter

Recommended explanations on Math Textbooks

Pure Maths

Statistics

Mechanics Maths

Applied Mathematics

Logic and Functions

Calculus

Study anywhere. Anytime. Across all devices.

Use the ratio test for absolute convergence to determine whether the series in Exercises 30鈥�35 converge absolutely or diverge.
${鈭�}_{k = 0}^{鈭�} \frac{{(- 2)}^{k} 1.3.5 . . . (2 k + 1)}{1.4.7 . . . (3 k + 1)}$