Proving That The Series is Convergent or Divergent

In summary, the conversation discusses a problem involving determining whether a series converges or diverges. The individual presents their solution using logarithms and asks for validation or a better method. Another individual offers a shorter and simpler approach using exponentials.
  • #1
jsewell94
23
0

Homework Statement



Determine whether the following series converges or diverges:
[itex]\sum_{}^{} ( \frac{1}{3} )^{ln(n)}[/itex]

Homework Equations



N/A

The Attempt at a Solution



See attached document..

I had my Calc 2 final today, and this was our hard problem...but I don't know if my method is valid or not. Could you help me determine if it is? And if it's not, could you tell me where the flaw in my reasoning is/a better method?
 

Attachments

  • Math Final Problem 15.pdf
    191.3 KB · Views: 208
Last edited:
Physics news on Phys.org
  • #2
jsewell94 said:

Homework Statement



Determine whether the following series converges or diverges:
[itex]\sum_{}^{} ( \frac{1}{3} )^{ln(n)}[/itex]

Homework Equations



N/A

The Attempt at a Solution



See attached document..

I had my Calc 2 final today, and this was our hard problem...but I don't know if my method is valid or not. Could you help me determine if it is? And if it's not, could you tell me where the flaw in my reasoning is/a better method?

It looks ok to me. You could shorten the whole argument up a lot. [itex]3^{ln(n)}=(e^{ln(3)})^{ln(n)}=e^{ln(3) ln(n)}=(e^{ln(n)})^{ln(3)}=n^{ln(3)}[/itex]. Just use ln(3) for k.
 
  • #3
Dick said:
It looks ok to me. You could shorten the whole argument up a lot. [itex]3^{ln(n)}=(e^{ln(3)})^{ln(n)}=e^{ln(3) ln(n)}=(e^{ln(n)})^{ln(3)}=n^{ln(3)}[/itex]. Just use ln(3) for k.

Oh wow, that makes sense!

Yeah, I just..couldn't figure out the easy way in the 15 minutes I had left on the test :(
Yay! That means I was the only one who got it :D
 

Related to Proving That The Series is Convergent or Divergent

What is the definition of a convergent series?

A convergent series is a series in which the sum of its terms approaches a finite limit as the number of terms increases.

What is the definition of a divergent series?

A divergent series is a series in which the sum of its terms does not approach a finite limit as the number of terms increases.

How do you prove that a series is convergent?

To prove that a series is convergent, you can use one of several methods, such as the comparison test, the ratio test, or the root test. These tests compare the given series to a known convergent series or use the properties of the terms to determine if the series is convergent.

How do you prove that a series is divergent?

To prove that a series is divergent, you can use the divergence test or the integral test. The divergence test states that if the limit of the terms of the series does not approach zero, then the series is divergent. The integral test compares the given series to an improper integral and determines if the integral is convergent or divergent.

What is the importance of determining if a series is convergent or divergent?

Determining if a series is convergent or divergent is important in many areas of mathematics and science. It helps us understand the behavior of infinite sums and can be used to solve various problems, such as finding the area under a curve or predicting the growth of a population. It also allows us to determine the validity of certain mathematical equations and models.

Similar threads

  • Calculus and Beyond Homework Help
Replies
2
Views
333
  • Calculus and Beyond Homework Help
Replies
8
Views
1K
  • Calculus and Beyond Homework Help
Replies
4
Views
1K
  • Calculus and Beyond Homework Help
Replies
2
Views
777
  • Calculus and Beyond Homework Help
Replies
7
Views
1K
  • Calculus and Beyond Homework Help
Replies
7
Views
2K
  • Calculus and Beyond Homework Help
Replies
11
Views
2K
Replies
8
Views
1K
  • Calculus and Beyond Homework Help
Replies
16
Views
1K
  • Calculus and Beyond Homework Help
Replies
29
Views
2K
Back
Top