∀ {E : Type u_2} {V₁ : Type u_4} {V₂ : Type u_3} {V₃ : Type u_1} [inst : LineDeriv E V₁ V₂] [inst_1 : LineDeriv E V₂ V₃]
  [inst_2 : AddCommGroup V₂] [inst_3 : AddCommGroup V₃] [inst_4 : AddCommGroup E] [LineDerivAdd E V₂ V₃] (f : V₁)
  (m₁ m₂ n : E),
  (fun x1 x2 => LineDeriv.lineDerivOp x1 (LineDeriv.lineDerivOp x2 f)) (m₁ + m₂) n =
    (fun x1 x2 => LineDeriv.lineDerivOp x1 (LineDeriv.lineDerivOp x2 f)) m₁ n +
      (fun x1 x2 => LineDeriv.lineDerivOp x1 (LineDeriv.lineDerivOp x2 f)) m₂ n