# Math Problem

**URL:** <https://forum.kirupa.com/t/math-problem/258699>\
**Category:** random\
**Created:** [April 26, 2008, 11:54pm UTC](https://forum.kirupa.com/t/math-problem/258699 "2008-04-26T23:54:04Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![Vexir](https://avatars.discourse-cdn.com/v4/letter/v/a183cd/32.png) [@Vexir](https://forum.kirupa.com/u/Vexir)\
**Post date:** [April 26, 2008, 11:54pm UTC](https://forum.kirupa.com/t/math-problem/258699/1 "2008-04-26T23:54:04Z")

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What is the radius of convergence of the series (n+1)(x-3)^n / (2n+1)(2^n). I use the ratio test, cancel things out, and I keep arriving at |(x-3)/2| \< 1, which gives me a radius of convergence of 3. However, this is not the correct answer.

The people in #math on Freenode are all AFK for some reason. 😛