The concept of geometric-arithmetic index was introduced in the chemical graph
theory recently, but it has shown to be useful. The aim of this paper is to obtain new
upper bounds of the geometric-arithmetic index and characterize graphs extremal
with respect to them.This research was supported by a grant from Agencia Estatal de Investigación (PID2019-106433GB-I00 / AEI / 10.13039/501100011033), Spain