Theorem: Polynomial.exists_unique_nilpotent_sub_and_aeval_eq_zero
File: Mathlib/Dynamics/Newton.lean

tactic: simp_rw [(neg_sub _ x).symm, isNilpotent_neg_iff]
state_before: R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
⊢ ∃! r, IsNilpotent (x - r) ∧ (aeval r) P = 0
state_after: R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
⊢ ∃! r, IsNilpotent (r - x) ∧ (aeval r) P = 0

tactic: refine exists_unique_of_exists_of_unique ?_ fun r₁ r₂ ⟨hr₁, hr₁'⟩ ⟨hr₂, hr₂'⟩ ↦ ?_
state_before: R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
⊢ ∃! r, IsNilpotent (r - x) ∧ (aeval r) P = 0
state_after: case refine_1
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
⊢ ∃ x_1, IsNilpotent (x_1 - x) ∧ (aeval x_1) P = 0

case refine_2
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
r₁ r₂ : S
x✝¹ : IsNilpotent (r₁ - x) ∧ (aeval r₁) P = 0
x✝ : IsNilpotent (r₂ - x) ∧ (aeval r₂) P = 0
hr₁ : IsNilpotent (r₁ - x)
hr₁' : (aeval r₁) P = 0
hr₂ : IsNilpotent (r₂ - x)
hr₂' : (aeval r₂) P = 0
⊢ r₁ = r₂

tactic: obtain ⟨n, hn⟩ := id h
state_before: case refine_1
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
⊢ ∃ x_1, IsNilpotent (x_1 - x) ∧ (aeval x_1) P = 0
state_after: case refine_1.intro
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
n : ℕ
hn : (aeval x) P ^ n = 0
⊢ ∃ x_1, IsNilpotent (x_1 - x) ∧ (aeval x_1) P = 0

tactic: refine ⟨P.newtonMap^[n] x, isNilpotent_iterate_newtonMap_sub_of_isNilpotent h n, ?_⟩
state_before: case refine_1.intro
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
n : ℕ
hn : (aeval x) P ^ n = 0
⊢ ∃ x_1, IsNilpotent (x_1 - x) ∧ (aeval x_1) P = 0
state_after: case refine_1.intro
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
n : ℕ
hn : (aeval x) P ^ n = 0
⊢ (aeval (P.newtonMap^[n] x)) P = 0

tactic: rw [← zero_dvd_iff, ← pow_eq_zero_of_le n.lt_two_pow.le hn]
state_before: case refine_1.intro
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
n : ℕ
hn : (aeval x) P ^ n = 0
⊢ (aeval (P.newtonMap^[n] x)) P = 0
state_after: case refine_1.intro
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
n : ℕ
hn : (aeval x) P ^ n = 0
⊢ (aeval x) P ^ 2 ^ n ∣ (aeval (P.newtonMap^[n] x)) P

tactic: exact aeval_pow_two_pow_dvd_aeval_iterate_newtonMap h h' n
state_before: case refine_1.intro
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
n : ℕ
hn : (aeval x) P ^ n = 0
⊢ (aeval x) P ^ 2 ^ n ∣ (aeval (P.newtonMap^[n] x)) P
state_after: no goals

tactic: have ⟨u, hu⟩ := binomExpansion (P.map (algebraMap R S)) r₁ (r₂ - r₁)
state_before: case refine_2
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
r₁ r₂ : S
x✝¹ : IsNilpotent (r₁ - x) ∧ (aeval r₁) P = 0
x✝ : IsNilpotent (r₂ - x) ∧ (aeval r₂) P = 0
hr₁ : IsNilpotent (r₁ - x)
hr₁' : (aeval r₁) P = 0
hr₂ : IsNilpotent (r₂ - x)
hr₂' : (aeval r₂) P = 0
⊢ r₁ = r₂
state_after: case refine_2
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
r₁ r₂ : S
x✝¹ : IsNilpotent (r₁ - x) ∧ (aeval r₁) P = 0
x✝ : IsNilpotent (r₂ - x) ∧ (aeval r₂) P = 0
hr₁ : IsNilpotent (r₁ - x)
hr₁' : (aeval r₁) P = 0
hr₂ : IsNilpotent (r₂ - x)
hr₂' : (aeval r₂) P = 0
u : S
hu :
  eval (r₁ + (r₂ - r₁)) (map (algebraMap R S) P) =
    eval r₁ (map (algebraMap R S) P) + eval r₁ (derivative (map (algebraMap R S) P)) * (r₂ - r₁) + u * (r₂ - r₁) ^ 2
⊢ r₁ = r₂

tactic: suffices IsUnit (aeval r₁ (derivative P) + u * (r₂ - r₁)) by
  rwa [derivative_map, eval_map_algebraMap, eval_map_algebraMap, eval_map_algebraMap,
    add_sub_cancel, hr₂', hr₁', zero_add, pow_two, ← mul_assoc, ← add_mul, eq_comm,
    this.mul_right_eq_zero, sub_eq_zero, eq_comm] at hu
state_before: case refine_2
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
r₁ r₂ : S
x✝¹ : IsNilpotent (r₁ - x) ∧ (aeval r₁) P = 0
x✝ : IsNilpotent (r₂ - x) ∧ (aeval r₂) P = 0
hr₁ : IsNilpotent (r₁ - x)
hr₁' : (aeval r₁) P = 0
hr₂ : IsNilpotent (r₂ - x)
hr₂' : (aeval r₂) P = 0
u : S
hu :
  eval (r₁ + (r₂ - r₁)) (map (algebraMap R S) P) =
    eval r₁ (map (algebraMap R S) P) + eval r₁ (derivative (map (algebraMap R S) P)) * (r₂ - r₁) + u * (r₂ - r₁) ^ 2
⊢ r₁ = r₂
state_after: case refine_2
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
r₁ r₂ : S
x✝¹ : IsNilpotent (r₁ - x) ∧ (aeval r₁) P = 0
x✝ : IsNilpotent (r₂ - x) ∧ (aeval r₂) P = 0
hr₁ : IsNilpotent (r₁ - x)
hr₁' : (aeval r₁) P = 0
hr₂ : IsNilpotent (r₂ - x)
hr₂' : (aeval r₂) P = 0
u : S
hu :
  eval (r₁ + (r₂ - r₁)) (map (algebraMap R S) P) =
    eval r₁ (map (algebraMap R S) P) + eval r₁ (derivative (map (algebraMap R S) P)) * (r₂ - r₁) + u * (r₂ - r₁) ^ 2
⊢ IsUnit ((aeval r₁) (derivative P) + u * (r₂ - r₁))

tactic: have : IsUnit (aeval r₁ (derivative P)) :=
  isUnit_aeval_of_isUnit_aeval_of_isNilpotent_sub h' hr₁
state_before: case refine_2
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
r₁ r₂ : S
x✝¹ : IsNilpotent (r₁ - x) ∧ (aeval r₁) P = 0
x✝ : IsNilpotent (r₂ - x) ∧ (aeval r₂) P = 0
hr₁ : IsNilpotent (r₁ - x)
hr₁' : (aeval r₁) P = 0
hr₂ : IsNilpotent (r₂ - x)
hr₂' : (aeval r₂) P = 0
u : S
hu :
  eval (r₁ + (r₂ - r₁)) (map (algebraMap R S) P) =
    eval r₁ (map (algebraMap R S) P) + eval r₁ (derivative (map (algebraMap R S) P)) * (r₂ - r₁) + u * (r₂ - r₁) ^ 2
⊢ IsUnit ((aeval r₁) (derivative P) + u * (r₂ - r₁))
state_after: case refine_2
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
r₁ r₂ : S
x✝¹ : IsNilpotent (r₁ - x) ∧ (aeval r₁) P = 0
x✝ : IsNilpotent (r₂ - x) ∧ (aeval r₂) P = 0
hr₁ : IsNilpotent (r₁ - x)
hr₁' : (aeval r₁) P = 0
hr₂ : IsNilpotent (r₂ - x)
hr₂' : (aeval r₂) P = 0
u : S
hu :
  eval (r₁ + (r₂ - r₁)) (map (algebraMap R S) P) =
    eval r₁ (map (algebraMap R S) P) + eval r₁ (derivative (map (algebraMap R S) P)) * (r₂ - r₁) + u * (r₂ - r₁) ^ 2
this : IsUnit ((aeval r₁) (derivative P))
⊢ IsUnit ((aeval r₁) (derivative P) + u * (r₂ - r₁))

tactic: rw [← sub_sub_sub_cancel_right r₂ r₁ x]
state_before: case refine_2
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
r₁ r₂ : S
x✝¹ : IsNilpotent (r₁ - x) ∧ (aeval r₁) P = 0
x✝ : IsNilpotent (r₂ - x) ∧ (aeval r₂) P = 0
hr₁ : IsNilpotent (r₁ - x)
hr₁' : (aeval r₁) P = 0
hr₂ : IsNilpotent (r₂ - x)
hr₂' : (aeval r₂) P = 0
u : S
hu :
  eval (r₁ + (r₂ - r₁)) (map (algebraMap R S) P) =
    eval r₁ (map (algebraMap R S) P) + eval r₁ (derivative (map (algebraMap R S) P)) * (r₂ - r₁) + u * (r₂ - r₁) ^ 2
this : IsUnit ((aeval r₁) (derivative P))
⊢ IsUnit ((aeval r₁) (derivative P) + u * (r₂ - r₁))
state_after: case refine_2
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
r₁ r₂ : S
x✝¹ : IsNilpotent (r₁ - x) ∧ (aeval r₁) P = 0
x✝ : IsNilpotent (r₂ - x) ∧ (aeval r₂) P = 0
hr₁ : IsNilpotent (r₁ - x)
hr₁' : (aeval r₁) P = 0
hr₂ : IsNilpotent (r₂ - x)
hr₂' : (aeval r₂) P = 0
u : S
hu :
  eval (r₁ + (r₂ - r₁)) (map (algebraMap R S) P) =
    eval r₁ (map (algebraMap R S) P) + eval r₁ (derivative (map (algebraMap R S) P)) * (r₂ - r₁) + u * (r₂ - r₁) ^ 2
this : IsUnit ((aeval r₁) (derivative P))
⊢ IsUnit ((aeval r₁) (derivative P) + u * (r₂ - x - (r₁ - x)))

tactic: refine IsNilpotent.isUnit_add_left_of_commute ?_ this (Commute.all _ _)
state_before: case refine_2
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
r₁ r₂ : S
x✝¹ : IsNilpotent (r₁ - x) ∧ (aeval r₁) P = 0
x✝ : IsNilpotent (r₂ - x) ∧ (aeval r₂) P = 0
hr₁ : IsNilpotent (r₁ - x)
hr₁' : (aeval r₁) P = 0
hr₂ : IsNilpotent (r₂ - x)
hr₂' : (aeval r₂) P = 0
u : S
hu :
  eval (r₁ + (r₂ - r₁)) (map (algebraMap R S) P) =
    eval r₁ (map (algebraMap R S) P) + eval r₁ (derivative (map (algebraMap R S) P)) * (r₂ - r₁) + u * (r₂ - r₁) ^ 2
this : IsUnit ((aeval r₁) (derivative P))
⊢ IsUnit ((aeval r₁) (derivative P) + u * (r₂ - x - (r₁ - x)))
state_after: case refine_2
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
r₁ r₂ : S
x✝¹ : IsNilpotent (r₁ - x) ∧ (aeval r₁) P = 0
x✝ : IsNilpotent (r₂ - x) ∧ (aeval r₂) P = 0
hr₁ : IsNilpotent (r₁ - x)
hr₁' : (aeval r₁) P = 0
hr₂ : IsNilpotent (r₂ - x)
hr₂' : (aeval r₂) P = 0
u : S
hu :
  eval (r₁ + (r₂ - r₁)) (map (algebraMap R S) P) =
    eval r₁ (map (algebraMap R S) P) + eval r₁ (derivative (map (algebraMap R S) P)) * (r₂ - r₁) + u * (r₂ - r₁) ^ 2
this : IsUnit ((aeval r₁) (derivative P))
⊢ IsNilpotent (u * (r₂ - x - (r₁ - x)))

tactic: exact (Commute.all _ _).isNilpotent_mul_right <| (Commute.all _ _).isNilpotent_sub hr₂ hr₁
state_before: case refine_2
R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
r₁ r₂ : S
x✝¹ : IsNilpotent (r₁ - x) ∧ (aeval r₁) P = 0
x✝ : IsNilpotent (r₂ - x) ∧ (aeval r₂) P = 0
hr₁ : IsNilpotent (r₁ - x)
hr₁' : (aeval r₁) P = 0
hr₂ : IsNilpotent (r₂ - x)
hr₂' : (aeval r₂) P = 0
u : S
hu :
  eval (r₁ + (r₂ - r₁)) (map (algebraMap R S) P) =
    eval r₁ (map (algebraMap R S) P) + eval r₁ (derivative (map (algebraMap R S) P)) * (r₂ - r₁) + u * (r₂ - r₁) ^ 2
this : IsUnit ((aeval r₁) (derivative P))
⊢ IsNilpotent (u * (r₂ - x - (r₁ - x)))
state_after: no goals

tactic: rwa [derivative_map, eval_map_algebraMap, eval_map_algebraMap, eval_map_algebraMap,
  add_sub_cancel, hr₂', hr₁', zero_add, pow_two, ← mul_assoc, ← add_mul, eq_comm,
  this.mul_right_eq_zero, sub_eq_zero, eq_comm] at hu
state_before: R : Type u_1
S : Type u_2
inst✝² : CommRing R
inst✝¹ : CommRing S
inst✝ : Algebra R S
P : R[X]
x : S
h : IsNilpotent ((aeval x) P)
h' : IsUnit ((aeval x) (derivative P))
r₁ r₂ : S
x✝¹ : IsNilpotent (r₁ - x) ∧ (aeval r₁) P = 0
x✝ : IsNilpotent (r₂ - x) ∧ (aeval r₂) P = 0
hr₁ : IsNilpotent (r₁ - x)
hr₁' : (aeval r₁) P = 0
hr₂ : IsNilpotent (r₂ - x)
hr₂' : (aeval r₂) P = 0
u : S
hu :
  eval (r₁ + (r₂ - r₁)) (map (algebraMap R S) P) =
    eval r₁ (map (algebraMap R S) P) + eval r₁ (derivative (map (algebraMap R S) P)) * (r₂ - r₁) + u * (r₂ - r₁) ^ 2
this : IsUnit ((aeval r₁) (derivative P) + u * (r₂ - r₁))
⊢ r₁ = r₂
state_after: no goals