Corollary of the M-test. Let EE be a set and let fn:ERf_n:E\to\mathbb R or fn:ECf_n:E\to\mathbb C be bounded functions. If

n=1fn\sum_{n=1}^\infty \|f_n\|_\infty

converges, where fn=supxEfn(x)\|f_n\|_\infty=\sup_{x\in E}|f_n(x)|, then n=1fn\sum_{n=1}^\infty f_n converges on EE and absolutely at each point.

Remarks

This is the with Mn=fnM_n=\|f_n\|_\infty.