Converging Series: Solve Sum of (3^n + 4^n) / (3^n + 5^n)

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SUMMARY

The series defined by the sum of (3^n + 4^n) / (3^n + 5^n) converges. By applying the comparison test, it is established that 3^n + 5^n is greater than 5^n, leading to the inequality 1/(3^n + 5^n) < 1/5^n. Consequently, the terms 3^n/(3^n + 5^n) and 4^n/(3^n + 5^n) can be bounded by (3/5)^n and (4/5)^n respectively, both of which are convergent geometric series.

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Homework Statement



Show that the following series converges:

Homework Equations



Sum of (from n=1 to infinity) of [3^n + 4^n] / [3^n + 5^n]

The Attempt at a Solution



Some help on this question would be much appreciated as i really don't know how to start it. Thanks
 
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What i would do is break the series into two. then by observing that:


3^n+5^n&gt;5^n=&gt;\frac{1}{3^n+5^n}&lt;\frac{1}{5^n}=&gt;\frac{3^n}{3^n+5^n}&lt;\left(\frac{3}{5}\right)^n


Also:

3^n+5^n&gt;5^n=&gt;... \frac{4^n}{3^n+5^n}&lt;\left(\frac{4}{5}\right)^n
 

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