Proving Divergence of the Series: \sum_{i=1}^{\infty}\sqrt{n+1}-\sqrt{n}

In summary: Homework Statement Prove that the series diverges: \sum_{i=1}^{\infty}\sqrt{n+1}-\sqrt{n}In summary, the series \sum_{i=1}^{\infty}\sqrt{n+1}-\sqrt{n} diverges and the comparison test can be used to prove it. By comparing the series with \frac{1}{\sqrt{n+1}+\sqrt{n+1}}, it can be shown that the original series has a larger value, indicating that it also diverges. Additionally, looking at the behavior of the terms for large values of n, it can be seen that they approach infinity, further supporting the divergence of the series.
  • #1
analysis001
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Homework Statement


Prove that the series diverges: [itex]\sum_{i=1}^{\infty}\sqrt{n+1}-\sqrt{n}[/itex]


The Attempt at a Solution


I'm trying to use the comparison test, but I don't know what to compare it to. All I have done so far is change the terms to be in fraction form:
[itex]\sqrt{n+1}[/itex]-[itex]\sqrt{n}[/itex]=[itex]\frac{1}{\sqrt{n+1}+\sqrt{n}}[/itex]

Any clues on what to do next would be great. Thanks!
 
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  • #2
analysis001 said:

Homework Statement


Prove that the series diverges: [itex]\sum_{i=1}^{\infty}\sqrt{n+1}-\sqrt{n}[/itex]


The Attempt at a Solution


I'm trying to use the comparison test, but I don't know what to compare it to. All I have done so far is change the terms to be in fraction form:
[itex]\sqrt{n+1}[/itex]-[itex]\sqrt{n}[/itex]=[itex]\frac{1}{\sqrt{n+1}+\sqrt{n}}[/itex]

Any clues on what to do next would be great. Thanks!

Try comparing with [itex]\frac{1}{\sqrt{n+1}+\sqrt{n+1}}[/itex]. Does that converge or diverge? How is it related to your original series?
 
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  • #3
analysis001 said:

Homework Statement


Prove that the series diverges: [itex]\sum_{i=1}^{\infty}\sqrt{n+1}-\sqrt{n}[/itex]


The Attempt at a Solution


I'm trying to use the comparison test, but I don't know what to compare it to. All I have done so far is change the terms to be in fraction form:
[itex]\sqrt{n+1}[/itex]-[itex]\sqrt{n}[/itex]=[itex]\frac{1}{\sqrt{n+1}+\sqrt{n}}[/itex]

Any clues on what to do next would be great. Thanks!

Look at the behavior of ## t_n \equiv \sqrt{n+1} - \sqrt{n}## for large ##n##. It helps to write
[tex] \sqrt{n+1} = \sqrt{n} \left( 1 + \frac{1}{n} \right)^{1/2} [/tex]
 

1. What is a "Divergent Series Proof"?

A "Divergent Series Proof" is a mathematical proof that shows a series (a sequence of numbers) does not have a finite sum. This means that as more terms are added to the series, the sum of the terms will continue to increase without ever reaching a specific value.

2. How is a "Divergent Series Proof" different from a regular proof?

In a regular proof, the goal is to show that a statement or equation is true. In a "Divergent Series Proof", the goal is to show that a series does not have a finite sum, which is considered a counterexample to the statement being true.

3. What is an example of a "Divergent Series Proof"?

An example of a "Divergent Series Proof" is the proof that the harmonic series, 1 + 1/2 + 1/3 + 1/4 + ..., does not have a finite sum. This was first shown by the mathematician Nicole Oresme in the 14th century.

4. Why are "Divergent Series Proofs" important in mathematics?

"Divergent Series Proofs" are important in mathematics because they demonstrate the limitations of certain mathematical concepts. They also open up new areas of study and research, as mathematicians seek to better understand these infinite series.

5. Can a "Divergent Series Proof" be used to prove a statement to be true?

No, a "Divergent Series Proof" can only show that a statement is false. If a series is proven to be divergent, it does not necessarily mean that the statement is true. It only means that the statement is not always true, as there may be exceptions where the series does have a finite sum.

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