SUMMARY
In this paper we extend previous results obtained in the framework of the Lagrangian formalism for the normal-state case to the superconducting state. The non-perturbative expansion applied to the generalized Hubbard model describing N-fold-degenerate correlated bands for large-N is considered. The standard Feynman diagrammatics is obtained and the renormalized physical quantities for this model are computed and analyzed. Our purpose is to obtain the 1/N corrections to the renormalized boson and fermion propagators for a state with Cooper-pair condensation.