high school Calculus B/C class homework:
1) Find a Series for f(x) = \frac{1}{1+x} then find the interval of convergence.
i know that \frac{1}{1+x} = 1-x+ x^{2}-x^{3}+...+ -x^{n}+... -1<x<1
but then i don`t understand how can i use the result from 1) to find 2) answer? since you guy will...