Homework Statement
If the nth partial sum of a series ##\sum_{n=1} ^\infty a_{n}## is
##S_{n} = \frac {n-1} {n+1}##
Find ##a_{n}## and ##\sum_{n=1}^\infty a_n##
Homework Equations
##S_{n} - S_{n-1}= a_{n}##
##\lim_{n \rightarrow +\infty} {S_{n}} = \sum_{n=1}^\infty a_n = S##
The Attempt at a...