Complete solution to a conjecture on Randic index

For a graph G, the Randic index R(G) of G is defined by , where d(u) is the degree of a vertex u and the summation runs over all edges uv of G. Let G(k,n) be the set of connected simple graphs of order n with minimum degree k. Bollobas and Erdos once asked for finding the minimum value of the Randic index among the graphs in G(k,n). There have been many partial solutions for this question. In this paper we give a complete solution to the question.