theorem lfneq2d (_G: wff) (F: set) (_n1 _n2: nat): $ _G -> _n1 = _n2 $ > $ _G -> lfn F _n1 = lfn F _n2 $;
_G -> F == F
_G -> _n1 = _n2
_G -> lfn F _n1 = lfn F _n2