The arithmetic-geometric index AG(G) and the geometric-arithmetic index
GA(G) of a graph G are defined as AG(G) = P uv∈E(G) dG(u)+dG(v)
2
√
dG(u)dG(v)
and
GA(G) =
P
uv∈E(G)
2
√
dG(u)dG(v)
dG(u)+dG(v) , where E(G) is the edge set of G, and dG(u)
and dG(v) are the degrees of vertices u and v, respectively. We study relations
between AG(G) and GA(G) for graphs G of given size, minimum degree and
maximum degree. We present lower and upper bounds on AG(G) + GA(G),
AG(G) − GA(G) and AG(G) · GA(G). All the bounds are sharp.