Bounds for the general sum-connectivity index of composite graphs

The general sum-connectivity index is a molecular descriptor defined as [Formula: see text] , where [Formula: see text] denotes the degree of a vertex [Formula: see text] , and α is a real number. Let X be a graph; then let [Formula: see text] be the graph obtained from X by adding a new vertex [Formula: see text] corresponding to each edge of X and joining [Formula: see text] to the end vertices of the corresponding edge [Formula: see text] . In this paper we obtain the lower and upper bounds for the general sum-connectivity index of four types of graph operations involving R-graph. Additionally, we determine the bounds for the general sum-connectivity index of line graph [Formula: see text] and rooted product of graphs.