Power series interval

1. Dec 10, 2007

frasifrasi

For summation from 1 to infinity of x^(n)/[2^(n)*n^(4)]
- I get the radius is 2 by ration test, but how do I get the interval, just by pluggin in?

2. Dec 10, 2007

frasifrasi

anyone? : )

3. Dec 10, 2007

rocomath

well it's just -1<x<1