文摘
The Randi? index R(G) of a graph G is the sum of the weights(d(u)d(v))-\frac12(d(u)d(v))^{-\frac{1}{2}} of all edges uv of G, where d(u) denotes the degree of the vertex u. In this paper, we first present a sharp lower bound on the Randi? index of conjugated unicyclic graphs (unicyclic graphs with perfect matching). Also a sharp lower bound on the Randi? index of unicyclic graphs is given in terms of the order and given size of matching.