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Sum or upped bound of geometrico-harmonic series

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aamir.ahmed
#1
Jun20-10, 05:15 PM
P: 2
Hi,
I need help to determine the upper bound of this infinite series.
[tex]\sum_{k=p+1}^{\infty} \frac{1}{k} a^k \ \ \ \ ; a \leq 1[/tex]

The paper I am reading reports the upper bound to be,
[tex]\sum_{k=p+1}^{\infty} \frac{1}{k} a^k \leq \frac{1}{p+1}\sum_{k=p+1}^{\infty} a^k = \frac{1}{p+1} \cdot \frac{a^{p+1}}{1-a}[/tex]

I totally cannot understand how could he factor 1/k coefficient out of the summation and replace it with 1/(p+1). Please point me in the right direction.
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CRGreathouse
#2
Jun20-10, 09:33 PM
Sci Advisor
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P: 3,682
Quote Quote by aamir.ahmed View Post
I totally cannot understand how could he factor 1/k coefficient out of the summation and replace it with 1/(p+1). Please point me in the right direction.
k is at least p+1, so 1/k is at most 1/(p+1).


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