New upper bounds on Zagreb indices

Abstract

The first Zagreb index M 1(G) is equal to the sum of squares of the degrees of the vertices, and the second Zagreb index M 2(G) is equal to the sum of the products of the degrees of pairs of adjacent vertices of the underlying molecular graph G. In this paper we obtain an upper bound on the first Zagreb index M 1(G) of G in terms of the number of vertices (n), number of edges (m), maximum vertex degree (Δ1), second maximum vertex degree (Δ2) and minimum vertex degree (δ). Using this result we find an upper bound on M 2(G). Moreover, we present upper bounds on M1(G) + M1(Ḡ) M 2(G) + M2(Ḡ) in terms of n, m, Δ1, Δ2, δ, where Ḡ denotes the complement of G. © 2008 Springer Science+Business Media, LLC.