-- Mathlib/Algebra/MvPolynomial/Basic.lean
@[simp]
lemma mul_monomial_mem_coeffsIn : p * monomial i 1 ∈ coeffsIn σ M ↔ p ∈ coeffsIn σ M

Proof state:
case mpr
R : Type u_2
S : Type u_3
σ : Type u_4
inst✝² : CommSemiring R
inst✝¹ : CommSemiring S
inst✝ : Module R S
M : Submodule R S
p : MvPolynomial σ S
i : σ →₀ ℕ
⊢ (∀ (i : σ →₀ ℕ), coeff i p ∈ M) → ∀ (i_1 : σ →₀ ℕ), (if i ≤ i_1 then coeff (i_1 - i) p * 1 else 0) ∈ M

Tactic:
rintro hp i

Result:
case mpr
R : Type u_2
S : Type u_3
σ : Type u_4
inst✝² : CommSemiring R
inst✝¹ : CommSemiring S
inst✝ : Module R S
M : Submodule R S
p : MvPolynomial σ S
i✝ : σ →₀ ℕ
hp : ∀ (i : σ →₀ ℕ), coeff i p ∈ M
i : σ →₀ ℕ
⊢ (if i✝ ≤ i then coeff (i - i✝) p * 1 else 0) ∈ M

Proof state:
case mp
R : Type u_2
S : Type u_3
σ : Type u_4
inst✝² : CommSemiring R
inst✝¹ : CommSemiring S
inst✝ : Module R S
M : Submodule R S
p : MvPolynomial σ S
i : σ →₀ ℕ
hp : ∀ (i_1 : σ →₀ ℕ), (if i ≤ i_1 then coeff (i_1 - i) p * 1 else 0) ∈ M
j : σ →₀ ℕ
⊢ coeff j p ∈ M

Tactic:
simpa using hp (j + i)

Result:
no goals

Proof state:
case mpr
R : Type u_2
S : Type u_3
σ : Type u_4
inst✝² : CommSemiring R
inst✝¹ : CommSemiring S
inst✝ : Module R S
M : Submodule R S
p : MvPolynomial σ S
i✝ : σ →₀ ℕ
hp : ∀ (i : σ →₀ ℕ), coeff i p ∈ M
i : σ →₀ ℕ
⊢ (if i✝ ≤ i then coeff (i - i✝) p * 1 else 0) ∈ M

Tactic:
split <;> simp [hp]

Result:
no goals

Proof state:
case mp
R : Type u_2
S : Type u_3
σ : Type u_4
inst✝² : CommSemiring R
inst✝¹ : CommSemiring S
inst✝ : Module R S
M : Submodule R S
p : MvPolynomial σ S
i : σ →₀ ℕ
⊢ (∀ (i_1 : σ →₀ ℕ), (if i ≤ i_1 then coeff (i_1 - i) p * 1 else 0) ∈ M) → ∀ (i : σ →₀ ℕ), coeff i p ∈ M

Tactic:
rintro hp j

Result:
case mp
R : Type u_2
S : Type u_3
σ : Type u_4
inst✝² : CommSemiring R
inst✝¹ : CommSemiring S
inst✝ : Module R S
M : Submodule R S
p : MvPolynomial σ S
i : σ →₀ ℕ
hp : ∀ (i_1 : σ →₀ ℕ), (if i ≤ i_1 then coeff (i_1 - i) p * 1 else 0) ∈ M
j : σ →₀ ℕ
⊢ coeff j p ∈ M

Proof state:
R : Type u_2
S : Type u_3
σ : Type u_4
inst✝² : CommSemiring R
inst✝¹ : CommSemiring S
inst✝ : Module R S
M : Submodule R S
p : MvPolynomial σ S
i : σ →₀ ℕ
⊢ p * (monomial i) 1 ∈ coeffsIn σ M ↔ p ∈ coeffsIn σ M

Tactic:
simp only [mem_coeffsIn, coeff_mul_monomial', Finsupp.mem_support_iff]

Result:
R : Type u_2
S : Type u_3
σ : Type u_4
inst✝² : CommSemiring R
inst✝¹ : CommSemiring S
inst✝ : Module R S
M : Submodule R S
p : MvPolynomial σ S
i : σ →₀ ℕ
⊢ (∀ (i_1 : σ →₀ ℕ), (if i ≤ i_1 then coeff (i_1 - i) p * 1 else 0) ∈ M) ↔ ∀ (i : σ →₀ ℕ), coeff i p ∈ M

Proof state:
R : Type u_2
S : Type u_3
σ : Type u_4
inst✝² : CommSemiring R
inst✝¹ : CommSemiring S
inst✝ : Module R S
M : Submodule R S
p : MvPolynomial σ S
i : σ →₀ ℕ
⊢ (∀ (i_1 : σ →₀ ℕ), (if i ≤ i_1 then coeff (i_1 - i) p * 1 else 0) ∈ M) ↔ ∀ (i : σ →₀ ℕ), coeff i p ∈ M

Tactic:
constructor

Result:
case mp
R : Type u_2
S : Type u_3
σ : Type u_4
inst✝² : CommSemiring R
inst✝¹ : CommSemiring S
inst✝ : Module R S
M : Submodule R S
p : MvPolynomial σ S
i : σ →₀ ℕ
⊢ (∀ (i_1 : σ →₀ ℕ), (if i ≤ i_1 then coeff (i_1 - i) p * 1 else 0) ∈ M) → ∀ (i : σ →₀ ℕ), coeff i p ∈ M

case mpr
R : Type u_2
S : Type u_3
σ : Type u_4
inst✝² : CommSemiring R
inst✝¹ : CommSemiring S
inst✝ : Module R S
M : Submodule R S
p : MvPolynomial σ S
i : σ →₀ ℕ
⊢ (∀ (i : σ →₀ ℕ), coeff i p ∈ M) → ∀ (i_1 : σ →₀ ℕ), (if i ≤ i_1 then coeff (i_1 - i) p * 1 else 0) ∈ M