The expression of the ground-state energy of an electron coupled simultaneo
usly with a Coulomb potential and a longitudinal-optical phonon held in par
abolic quantum dots and wires is derived within the framework of Feynman va
riational path-integral theory. We obtain a general result with arbitrary e
lectron-phonon coupling constant, Coulomb binding parameters, and confining
potential strength, which could be used for further numerical calculation
of polaron properties. Moreover, it is shown that ah the previous path-inte
gral formulae for free polarons, bound polarons, and polarons confined in p
arabolic quantum dots and wires can be recovered in the present formalism.