∀ {R : Type u} {A : Type v} {B : Type w} [inst : CommSemiring R] [inst_1 : Semiring A] [inst_2 : Algebra R A]
  [inst_3 : Semiring B] [inst_4 : Algebra R B] (f : A →ₐ[R] B) (S : Subalgebra R A), ↑(Subalgebra.map f S) = ⇑f '' ↑S