∀ {R : Type u_1} {A : Type u_2} [inst : CommRing R] [inst_1 : BinomialRing R] [inst_2 : Ring A] [inst_3 : Algebra R A]
  (r s : R), PowerSeries.binomialSeries A (r + s) = PowerSeries.binomialSeries A r * PowerSeries.binomialSeries A s