Convergence of series using ratio test

Click For Summary
SUMMARY

The discussion centers on proving the convergence of the series summation of sqrt(An)/n, given that the series summation of An converges with all An > 0. The ratio test was initially applied, where Bn was defined as sqrt(An)/n. However, it was concluded that the ratio test is ineffective since the limit of the ratio of consecutive terms approaches 1, indicating that further convergence tests are necessary. Participants suggested exploring alternative convergence tests beyond the ratio test.

PREREQUISITES
  • Understanding of convergence tests in series, specifically the Ratio Test.
  • Familiarity with limits and their properties in calculus.
  • Knowledge of sequences and series, particularly the behavior of An as n approaches infinity.
  • Basic proficiency in mathematical notation and manipulation of inequalities.
NEXT STEPS
  • Research the Comparison Test for series convergence.
  • Learn about the Root Test and its application in determining series convergence.
  • Explore the Integral Test for series convergence analysis.
  • Investigate the Limit Comparison Test and its effectiveness in series evaluation.
USEFUL FOR

Students studying calculus, particularly those focusing on series convergence, as well as educators seeking to enhance their understanding of convergence tests and their applications in mathematical analysis.

l888l888l888
Messages
49
Reaction score
0

Homework Statement


assume summation of series An converges with all An>0. Prove summation of sqrt(An)/n converges

Homework Equations





The Attempt at a Solution


I Tried using the ratio test which says if lim as n goes to infinity of |Bn+1/Bn|<1 then summation of Bn converges. I let Bn be Sqrt(An)/n and we have...

lim as n goes to infinity of |(sqrt(An+1/An)*n/n+1|. limit of n/n+1 goes to one so i need to prove that |sqrt(An+1/An)|<1. But I got stuck because just because An converges does not mean that |(An+1/An)|<1. Can someone help me or suggest on a different convergence test that I should use?
 
Physics news on Phys.org
For your series,
\lim_{n \to \infty} \sqrt{\frac{a_{n+1}}{a_n}} = 1

so the Ratio Test is not going to be any help.

What other tests do you know?
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 4 ·
Replies
4
Views
1K