What did i do wrong? Ratio and comparison test question?

  • Thread starter rickyram
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  • #1
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Homework Statement



The summation of n/lnn from n=1 to infinity

Homework Equations



Ratio and Comparison test


The Attempt at a Solution



http://i55.tinypic.com/2jxuue.jpg

Alright so the way labeled "right way" on the picture is the right way according to the book but isn't the way I did with the ratio test right also? What did i do wrong?
 

Answers and Replies

  • #2
22,089
3,297
It is NOT true that

[tex]\frac{ln(n+1)}{ln(n)}=ln(1) [/tex]
 
  • #3
351
1
ln (n+1) / ln (n) isn't ln(1), in the limit or otherwise.
 
  • #4
2
0
Oh man, I gotta brush up on my logarithm rules... Anyway thanks for answerin my question, it has been a big help.
 
  • #5
Apply the divergence test directly. take limit n->(infinity) n/lnn. I doubt that goes to zero!
 

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