摘要
The energy of a graph is the sum of the absolute values of the eigenvalues of its adjacency matrix. Let be the set of trees with given order k. Suppose that and be the ordering vertex set of T. We denote by the graph obtained by attaching pendent vertices to vertex of T respectively. Let . In this paper, we determine the trees in with the first and the second minimal energies. As applications, we can characterize the trees with the first and the second minimal energies among the set of trees with given domination number, matching number, independence number respectively.