Testing Absolute Convergence of ∑(-2)n+1/n+5n

In summary, the series ∑ (-2)^n+1/(n+5^n) is being tested for absolute convergence. The comparison test can be used, with the series ∑ 2^n/5^n as the comparison series. The correct notation for the series is ∑ (-2)^(n+1)/(n+5^n), with parentheses around the exponent to avoid ambiguity.
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∑ (-2)n+1/n+5n Test this series Absolute Convergence ?

∑|an| = ∑(2)n+1/n+5n

if the sum of |an| converges, than the sum of an converges

∑|an| = ∑(2)n+1/n+5n

I can use Comparison Test?
I can choose series bn = ∑ 2n/5n ?
 
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Please don't delete the homework template.

Do you mean ##\displaystyle \sum \frac{(-2)^{n+1}}{n+5^n}##? Then you need brackets around the denominator. If that is your series, you can use this comparison.
 
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Another said:
∑ (-2)n+1/n+5n Test this series Absolute Convergence ?

∑|an| = ∑(2)n+1/n+5n

if the sum of |an| converges, than the sum of an converges

∑|an| = ∑(2)n+1/n+5n

I can use Comparison Test?
I can choose series bn = ∑ 2n/5n ?

What you wrote is obviously divergent: your series has
$$a_n = \frac{(-2)^{n+1}}{n} + 5^n,$$
giving two divergent series.

Perhaps you meant
$$a_n = \frac{(-2)^{n+1}}{n+5^n},$$
but that is not what you wrote. You need parentheses: just write (-2)^(n+1)/(n+5^n), and the problem would go away!
 
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1. What is the purpose of testing absolute convergence?

The purpose of testing absolute convergence is to determine if a given series converges or diverges. This is important in mathematics and science as it helps us understand the behavior and properties of different series.

2. How do you test for absolute convergence?

To test for absolute convergence, we use the ratio test or the root test. These tests compare the given series to a geometric series and determine if it converges or diverges. If the limit of the ratio or root is less than 1, the series converges absolutely. If the limit is greater than 1, the series diverges. If the limit is equal to 1, the test is inconclusive and another method may be needed.

3. What is the formula for the ratio test?

The formula for the ratio test is:
limn→∞ |an+1/an|
where an is the nth term of the series.

4. Can the ratio or root test be used for all series?

No, the ratio and root tests can only be used for series with positive terms. If the series has negative terms, the alternating series test or another method must be used.

5. What is the difference between absolute convergence and conditional convergence?

Absolute convergence means that a series converges regardless of the order of its terms. Conditional convergence means that a series only converges if its terms are arranged in a specific order. For example, the alternating harmonic series converges conditionally, but not absolutely.

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