Summation series

  • Thread starter cloveryeah
  • Start date
  • #1
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0

Homework Statement



Σ ( x^n/ln(n+5) )
n=1

find the value of x that the above series converges

Homework Equations




The Attempt at a Solution


i cal. it by ratio test
and i found that |x|<1

but when i input (-1,1) into my webwork...it said it's wrong[/B]
 

Answers and Replies

  • #2
Ray Vickson
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Homework Statement



Σ ( x^n/ln(n+5) )
n=1

find the value of x that the above series converges

Homework Equations




The Attempt at a Solution


i cal. it by ratio test
and i found that |x|<1

but when i input (-1,1) into my webwork...it said it's wrong[/B]

Your answer may be overly conservative. You need to look at whether the series converges or diverges at x = +1 and at x = -1.
 
  • #3
224
35
Hi Cloveryeah,
Great work, just something you've missed
In order for the series to converge,
Whenver n→∞ (x^n/ln(n+5)) = 0
You said that |x| < 1, you can't try x= 1 or x = -1, it's strictly less not even equal
 

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