Sunday, 28 April 2013

calculus - Infinite sum convergence test.



I have to tell if the sum n=1(1)n1n+(1)n+1
Converges or not. Can i use a comprasion test here? To assume that my sum is bigger than n=1(1)n1n+1? I dont think that's OK, but that's the only way I can think of right now.


Answer



How about this? Write out the series:
1(11+1)+1(121)1(13+1)+1(141)1(15+1)....
=12+114+1316+1518....

Then reorder terms...
112+1314+1516...
And it was the alternating harmonic series all along! Which has been proven to equal
n=1(1)n+11n=ln(2)


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