∀ (K : Type u_1) [inst : CommRing K] [inst_1 : IsDomain K] (R : Type u_2) [inst_2 : CommSemiring R]
  [inst_3 : Algebra R (Polynomial K)] (x y : R),
  RatFunc.mk ((algebraMap R (Polynomial K)) (x + y)) 1 =
    RatFunc.mk ((algebraMap R (Polynomial K)) x) 1 + RatFunc.mk ((algebraMap R (Polynomial K)) y) 1