Module: Mathlib.RingTheory.Jacobson.Ring

Goal state before:
pp: case refine_1.inl
R : Type u_1
inst✝⁶ : CommRing R
Rₘ : Type u_3
Sₘ : Type u_4
inst✝⁵ : CommRing Rₘ
inst✝⁴ : CommRing Sₘ
P : Ideal R[X]
pX : R[X]
hpX : pX ∈ P
inst✝³ : Algebra (R ⧸ comap C P) Rₘ
inst✝² : IsLocalization.Away (map (Ideal.Quotient.mk (comap C P)) pX).leadingCoeff Rₘ
inst✝¹ : Algebra (R[X] ⧸ P) Sₘ
inst✝ :
  IsLocalization
    (Submonoid.map (quotientMap P C ⋯) (Submonoid.powers (map (Ideal.Quotient.mk (comap C P)) pX).leadingCoeff)) Sₘ
P' : Ideal R := comap C P
M : Submonoid (R ⧸ P') := Submonoid.powers (map (Ideal.Quotient.mk (comap C P)) pX).leadingCoeff
M' : Submonoid (R[X] ⧸ P) :=
  Submonoid.map (quotientMap P C ⋯) (Submonoid.powers (map (Ideal.Quotient.mk (comap C P)) pX).leadingCoeff)
φ : R ⧸ P' →+* R[X] ⧸ P := quotientMap P C ⋯
φ' : Rₘ →+* Sₘ := IsLocalization.map Sₘ φ ⋯
hφ' : φ.comp (Ideal.Quotient.mk P') = (Ideal.Quotient.mk P).comp C
p✝ : Sₘ
p' q : R[X] ⧸ P
hq : q ∈ M'
hp : p✝ * (algebraMap (R[X] ⧸ P) Sₘ) q = (algebraMap (R[X] ⧸ P) Sₘ) p'
p : R[X]
hy : p = X
⊢ φ'.IsIntegralElem (((algebraMap (R[X] ⧸ P) Sₘ).comp (Ideal.Quotient.mk P)) p)

pp: case refine_1.inr
R : Type u_1
inst✝⁶ : CommRing R
Rₘ : Type u_3
Sₘ : Type u_4
inst✝⁵ : CommRing Rₘ
inst✝⁴ : CommRing Sₘ
P : Ideal R[X]
pX : R[X]
hpX : pX ∈ P
inst✝³ : Algebra (R ⧸ comap C P) Rₘ
inst✝² : IsLocalization.Away (map (Ideal.Quotient.mk (comap C P)) pX).leadingCoeff Rₘ
inst✝¹ : Algebra (R[X] ⧸ P) Sₘ
inst✝ :
  IsLocalization
    (Submonoid.map (quotientMap P C ⋯) (Submonoid.powers (map (Ideal.Quotient.mk (comap C P)) pX).leadingCoeff)) Sₘ
P' : Ideal R := comap C P
M : Submonoid (R ⧸ P') := Submonoid.powers (map (Ideal.Quotient.mk (comap C P)) pX).leadingCoeff
M' : Submonoid (R[X] ⧸ P) :=
  Submonoid.map (quotientMap P C ⋯) (Submonoid.powers (map (Ideal.Quotient.mk (comap C P)) pX).leadingCoeff)
φ : R ⧸ P' →+* R[X] ⧸ P := quotientMap P C ⋯
φ' : Rₘ →+* Sₘ := IsLocalization.map Sₘ φ ⋯
hφ' : φ.comp (Ideal.Quotient.mk P') = (Ideal.Quotient.mk P).comp C
p✝ : Sₘ
p' q : R[X] ⧸ P
hq : q ∈ M'
hp : p✝ * (algebraMap (R[X] ⧸ P) Sₘ) q = (algebraMap (R[X] ⧸ P) Sₘ) p'
p : R[X]
hy : p.degree ≤ 0
⊢ φ'.IsIntegralElem (((algebraMap (R[X] ⧸ P) Sₘ).comp (Ideal.Quotient.mk P)) p)

Tactic:
· rw [hy]
      refine φ.isIntegralElem_localization_at_leadingCoeff ((Ideal.Quotient.mk P) X)
        (pX.map (Ideal.Quotient.mk P')) ?_ M ?_
      · rwa [eval₂_map, hφ', ← hom_eval₂, Quotient.eq_zero_iff_mem, eval₂_C_X]
      · use 1
        simp only [P', pow_one]

Goal state after:
case refine_1.inr
R : Type u_1
inst✝⁶ : CommRing R
Rₘ : Type u_3
Sₘ : Type u_4
inst✝⁵ : CommRing Rₘ
inst✝⁴ : CommRing Sₘ
P : Ideal R[X]
pX : R[X]
hpX : pX ∈ P
inst✝³ : Algebra (R ⧸ comap C P) Rₘ
inst✝² : IsLocalization.Away (map (Ideal.Quotient.mk (comap C P)) pX).leadingCoeff Rₘ
inst✝¹ : Algebra (R[X] ⧸ P) Sₘ
inst✝ :
  IsLocalization
    (Submonoid.map (quotientMap P C ⋯) (Submonoid.powers (map (Ideal.Quotient.mk (comap C P)) pX).leadingCoeff)) Sₘ
P' : Ideal R := comap C P
M : Submonoid (R ⧸ P') := Submonoid.powers (map (Ideal.Quotient.mk (comap C P)) pX).leadingCoeff
M' : Submonoid (R[X] ⧸ P) :=
  Submonoid.map (quotientMap P C ⋯) (Submonoid.powers (map (Ideal.Quotient.mk (comap C P)) pX).leadingCoeff)
φ : R ⧸ P' →+* R[X] ⧸ P := quotientMap P C ⋯
φ' : Rₘ →+* Sₘ := IsLocalization.map Sₘ φ ⋯
hφ' : φ.comp (Ideal.Quotient.mk P') = (Ideal.Quotient.mk P).comp C
p✝ : Sₘ
p' q : R[X] ⧸ P
hq : q ∈ M'
hp : p✝ * (algebraMap (R[X] ⧸ P) Sₘ) q = (algebraMap (R[X] ⧸ P) Sₘ) p'
p : R[X]
hy : p.degree ≤ 0
⊢ φ'.IsIntegralElem (((algebraMap (R[X] ⧸ P) Sₘ).comp (Ideal.Quotient.mk P)) p)