Prove Cauchy's Convergence Criterion.
So I need to show that the partial sum $s_{n}=\sum^{n}_{i=0}a_{i}$ is Cauchy. $\rightarrow\forall\epsilon>0,\exists N$ s.t. $\forall n,m>N |s_m-s_n|<\epsilon$.
My guess is that I look at the fact that $s_n=\sum^{n} |s_n|=|a_{1}+...+a_{n}|$ and find a way to get $|s_m-s_n|<\epsilon$.