In the present paper we discuss the limits and the correct utilization of the standard program for the inversion of the Eliashberg equations, and the determination of the electron-phonon spectral function and the Coulomb pseudopotential from tunneling measurements in high-T c superconductors. In order to compare the calculated density of states with the experimental one, we introduce the results of the inversion procedure, applied to our recent tunneling data in Bi 2 Sr 2 CaCu 2 O 8 + x single-crystal break junctions with T c = 93 K, in a direct program for the solution of the Eliashberg equations. Most of the observed differences between theoretical and experimental curves at energy greater than the gap can be explained by a smooth energy dependence of the normal density of states that we introduced in the direct solution of the Eliashberg equations. Finally we show that the effects of the energy-dependent normal density of states can be simulated by an efficient electron-phonon spectral function but, also, by a negative, nonphysical, Coulomb pseudopotential.