Series converge/ diverges. determine sum of series

  • Thread starter Thread starter mattmannmf
  • Start date Start date
  • Tags Tags
    Series Sum
AI Thread Summary
The series in question is the sum of 2/n(n+2) from n=1 to infinity. The initial approach used partial fractions leading to a telescoping series, but the decomposition was incorrect. After correcting the error, the series converges, and the correct sum is determined to be 3/2. The discussion highlights the importance of accurate partial fraction decomposition in series analysis. Overall, the series converges with the final sum confirmed as 3/2.
mattmannmf
Messages
170
Reaction score
0
Determine if the series converges or diverges ad if it converges then determine the sum of the series analytically:

infinity
{Sigma} 2/n(n+2)
n=1

so i used partial fractions and got:
{Sigma} [1/n + 1/(n+2)]

then i used telescoping form to get the nth partial sum...
Sn= (1/1 + 1/3) + (1/2 + 1/4) +...

then i got the nth partial sum to be = 1+1/(n+2)

so the series converges and its sum is 1?

Does that seem right to everyone?
 
Mathematics news on Phys.org
First, this is in the wrong section, I believe. It should go in the homework and coursework area.

Second, yes. However, be careful...

As you did the work wrong, and yet got the right answer. The partial fraction decomposition for \frac{2}{(n)(n+2)} isn't quite what you posted. Can you see the error?
 
oh ok. i thought this was the homework and course area.

yea its supposed to be subtraction, not addition. i got 3/2 to be the sum of the series
 
There you go.

You win...
 
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. In Dirac’s Principles of Quantum Mechanics published in 1930 he introduced a “convenient notation” he referred to as a “delta function” which he treated as a continuum analog to the discrete Kronecker delta. The Kronecker delta is simply the indexed components of the identity operator in matrix algebra Source: https://www.physicsforums.com/insights/what-exactly-is-diracs-delta-function/ by...
Suppose ,instead of the usual x,y coordinate system with an I basis vector along the x -axis and a corresponding j basis vector along the y-axis we instead have a different pair of basis vectors ,call them e and f along their respective axes. I have seen that this is an important subject in maths My question is what physical applications does such a model apply to? I am asking here because I have devoted quite a lot of time in the past to understanding convectors and the dual...
Thread 'Imaginary Pythagoras'
I posted this in the Lame Math thread, but it's got me thinking. Is there any validity to this? Or is it really just a mathematical trick? Naively, I see that i2 + plus 12 does equal zero2. But does this have a meaning? I know one can treat the imaginary number line as just another axis like the reals, but does that mean this does represent a triangle in the complex plane with a hypotenuse of length zero? Ibix offered a rendering of the diagram using what I assume is matrix* notation...

Similar threads

Replies
7
Views
2K
Replies
0
Views
2K
Replies
20
Views
2K
Replies
12
Views
1K
Replies
8
Views
3K
Replies
5
Views
2K
Replies
10
Views
2K
Back
Top