Module: Mathlib.Algebra.Algebra.NonUnitalSubalgebra

Goal state before:
pp: case refine_2
F : Type u_1
R : Type u
A : Type v
B : Type w
inst✝⁸ : CommSemiring R
inst✝⁷ : NonUnitalNonAssocSemiring A
inst✝⁶ : Module R A
inst✝⁵ : NonUnitalNonAssocSemiring B
inst✝⁴ : Module R B
inst✝³ : FunLike F A B
inst✝² : NonUnitalAlgHomClass F R A B
inst✝¹ : IsScalarTower R A A
inst✝ : SMulCommClass R A A
s : Set A
a b : A
ha : a ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s)
hb : b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s)
⊢ 0 * b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s)

pp: case refine_3
F : Type u_1
R : Type u
A : Type v
B : Type w
inst✝⁸ : CommSemiring R
inst✝⁷ : NonUnitalNonAssocSemiring A
inst✝⁶ : Module R A
inst✝⁵ : NonUnitalNonAssocSemiring B
inst✝⁴ : Module R B
inst✝³ : FunLike F A B
inst✝² : NonUnitalAlgHomClass F R A B
inst✝¹ : IsScalarTower R A A
inst✝ : SMulCommClass R A A
s : Set A
a b : A
ha : a ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s)
hb : b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s)
⊢ ∀ (x y : A),
    x ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s) →
      y ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s) →
        x * b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s) →
          y * b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s) →
            (x + y) * b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s)

pp: case refine_4
F : Type u_1
R : Type u
A : Type v
B : Type w
inst✝⁸ : CommSemiring R
inst✝⁷ : NonUnitalNonAssocSemiring A
inst✝⁶ : Module R A
inst✝⁵ : NonUnitalNonAssocSemiring B
inst✝⁴ : Module R B
inst✝³ : FunLike F A B
inst✝² : NonUnitalAlgHomClass F R A B
inst✝¹ : IsScalarTower R A A
inst✝ : SMulCommClass R A A
s : Set A
a b : A
ha : a ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s)
hb : b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s)
⊢ ∀ (a : R),
    ∀ x ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s),
      x * b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s) →
        a • x * b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s)

Tactic:
· exact (zero_mul b).symm ▸ Submodule.zero_mem _

Goal state after:
case refine_3
F : Type u_1
R : Type u
A : Type v
B : Type w
inst✝⁸ : CommSemiring R
inst✝⁷ : NonUnitalNonAssocSemiring A
inst✝⁶ : Module R A
inst✝⁵ : NonUnitalNonAssocSemiring B
inst✝⁴ : Module R B
inst✝³ : FunLike F A B
inst✝² : NonUnitalAlgHomClass F R A B
inst✝¹ : IsScalarTower R A A
inst✝ : SMulCommClass R A A
s : Set A
a b : A
ha : a ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s)
hb : b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s)
⊢ ∀ (x y : A),
    x ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s) →
      y ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s) →
        x * b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s) →
          y * b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s) →
            (x + y) * b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s)

case refine_4
F : Type u_1
R : Type u
A : Type v
B : Type w
inst✝⁸ : CommSemiring R
inst✝⁷ : NonUnitalNonAssocSemiring A
inst✝⁶ : Module R A
inst✝⁵ : NonUnitalNonAssocSemiring B
inst✝⁴ : Module R B
inst✝³ : FunLike F A B
inst✝² : NonUnitalAlgHomClass F R A B
inst✝¹ : IsScalarTower R A A
inst✝ : SMulCommClass R A A
s : Set A
a b : A
ha : a ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s)
hb : b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s)
⊢ ∀ (a : R),
    ∀ x ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s),
      x * b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s) →
        a • x * b ∈ Submodule.span R ↑(NonUnitalSubsemiring.closure s)