∀ {R : Type u_2} {A : Type u_3} {B : Type u_1} [inst : CommSemiring R] [inst_1 : Semiring A] [inst_2 : Algebra R A]
  [inst_3 : StarRing A] [inst_4 : Semiring B] [inst_5 : Algebra R B] [inst_6 : StarRing B] (f : A →⋆ₐ[R] B)
  (hf : Function.Injective ⇑f) (x y : A),
  (AlgEquiv.ofInjective (↑f) hf).toFun (x * y) =
    (AlgEquiv.ofInjective (↑f) hf).toFun x * (AlgEquiv.ofInjective (↑f) hf).toFun y