mathlib-initiative/mathlib-tactics huggingface dataset:
Module: Mathlib.LinearAlgebra.Matrix.SchurComplement

Goal state before:
pp: case neg
m : Type u_2
n : Type u_3
α : Type u_4
inst✝⁴ : Fintype m
inst✝³ : Fintype n
inst✝² : DecidableEq m
inst✝¹ : DecidableEq n
inst✝ : CommRing α
A : Matrix m m α
B : Matrix m n α
D : Matrix n n α
hAD : IsUnit A ↔ IsUnit D
hA : ¬IsUnit A
⊢ (fromBlocks A B 0 D)⁻¹ = fromBlocks A⁻¹ (-(A⁻¹ * B * D⁻¹)) 0 D⁻¹

Tactic:
· have hD := hAD.not.mp hA
    have : ¬IsUnit (fromBlocks A B 0 D) :=
      isUnit_fromBlocks_zero₂₁.not.mpr (not_and'.mpr fun _ => hA)
    simp_rw [nonsing_inv_eq_ringInverse, Ring.inverse_non_unit _ hA, Ring.inverse_non_unit _ hD,
      Ring.inverse_non_unit _ this, Matrix.zero_mul, neg_zero, fromBlocks_zero]

Goal state after:
Module: Mathlib.LinearAlgebra.Matrix.Charpoly.Basic

Goal state before:
pp: R : Type u_1
inst✝⁴ : CommRing R
m : Type u_3
n : Type u_4
inst✝³ : DecidableEq m
inst✝² : DecidableEq n
inst✝¹ : Fintype m
inst✝ : Fintype n
A : Matrix m n R
B : Matrix n m R
M : Matrix (m ⊕ n) (m ⊕ n) R[X] := fromBlocks ((scalar m) X) (A.map ⇑C) (B.map ⇑C) 1
N : Matrix (m ⊕ n) (m ⊕ n) R[X] := fromBlocks (-1) 0 (B.map ⇑C) (-(scalar n) X)
hMN : M * N = fromBlocks (-(scalar m) X + (A * B).map ⇑C) (-X • A.map ⇑C) 0 (-(scalar n) X)
hNM : N * M = fromBlocks (-(scalar m) X) (-A.map ⇑C) 0 ((B * A).map ⇑C - (scalar n) X)
hdet_MN :
  (M * N).det = (-1) ^ (Fintype.card m + Fintype.card n) * (X ^ Fintype.card n * ((scalar m) X - (A * B).map ⇑C).det)
hdet_NM :
  (N * M).det = (-1) ^ (Fintype.card m + Fintype.card n) * (X ^ Fintype.card m * ((scalar n) X - (B * A).map ⇑C).det)
⊢ (-1) ^ ?m.456 * (X ^ Fintype.card n * ((scalar m) X - (A * B).map ⇑C).det) =
    (-1) ^ ?m.456 * (X ^ Fintype.card m * ((scalar n) X - (B * A).map ⇑C).det)

pp: R : Type u_1
inst✝⁴ : CommRing R
m : Type u_3
n : Type u_4
inst✝³ : DecidableEq m
inst✝² : DecidableEq n
inst✝¹ : Fintype m
inst✝ : Fintype n
A : Matrix m n R
B : Matrix n m R
M : Matrix (m ⊕ n) (m ⊕ n) R[X] := ⋯
N : Matrix (m ⊕ n) (m ⊕ n) R[X] := ⋯
hMN : M * N = fromBlocks (-(scalar m) X + (A * B).map ⇑C) (-X • A.map ⇑C) 0 (-(scalar n) X)
hNM : N * M = fromBlocks (-(scalar m) X) (-A.map ⇑C) 0 ((B * A).map ⇑C - (scalar n) X)
hdet_MN :
  (M * N).det = (-1) ^ (Fintype.card m + Fintype.card n) * (X ^ Fintype.card n * ((scalar m) X - (A * B).map ⇑C).det)
hdet_NM :
  (N * M).det = (-1) ^ (Fintype.card m + Fintype.card n) * (X ^ Fintype.card m * ((scalar n) X - (B * A).map ⇑C).det)
⊢ ℕ

Tactic:
← hdet_NM,

Goal state after:
R : Type u_1
inst✝⁴ : CommRing R
m : Type u_3
n : Type u_4
inst✝³ : DecidableEq m
inst✝² : DecidableEq n
inst✝¹ : Fintype m
inst✝ : Fintype n
A : Matrix m n R
B : Matrix n m R
M : Matrix (m ⊕ n) (m ⊕ n) R[X] := fromBlocks ((scalar m) X) (A.map ⇑C) (B.map ⇑C) 1
N : Matrix (m ⊕ n) (m ⊕ n) R[X] := fromBlocks (-1) 0 (B.map ⇑C) (-(scalar n) X)
hMN : M * N = fromBlocks (-(scalar m) X + (A * B).map ⇑C) (-X • A.map ⇑C) 0 (-(scalar n) X)
hNM : N * M = fromBlocks (-(scalar m) X) (-A.map ⇑C) 0 ((B * A).map ⇑C - (scalar n) X)
hdet_MN :
  (M * N).det = (-1) ^ (Fintype.card m + Fintype.card n) * (X ^ Fintype.card n * ((scalar m) X - (A * B).map ⇑C).det)
hdet_NM :
  (N * M).det = (-1) ^ (Fintype.card m + Fintype.card n) * (X ^ Fintype.card m * ((scalar n) X - (B * A).map ⇑C).det)
⊢ (-1) ^ (Fintype.card m + Fintype.card n) * (X ^ Fintype.card n * ((scalar m) X - (A * B).map ⇑C).det) = (N * M).det
Module: Mathlib.LinearAlgebra.Matrix.SchurComplement

Goal state before:
pp: case neg
m : Type u_2
n : Type u_3
α : Type u_4
inst✝⁴ : Fintype m
inst✝³ : Fintype n
inst✝² : DecidableEq m
inst✝¹ : DecidableEq n
inst✝ : CommRing α
A : Matrix m m α
C : Matrix n m α
D : Matrix n n α
hAD : IsUnit A ↔ IsUnit D
hA : ¬IsUnit A
hD : ¬IsUnit D
this : ¬IsUnit (fromBlocks A 0 C D)
⊢ (fromBlocks A 0 C D)⁻¹ = fromBlocks A⁻¹ 0 (-(D⁻¹ * C * A⁻¹)) D⁻¹

Tactic:
simp_rw [nonsing_inv_eq_ringInverse, Ring.inverse_non_unit _ hA, Ring.inverse_non_unit _ hD,
      Ring.inverse_non_unit _ this, Matrix.zero_mul, neg_zero, fromBlocks_zero]

Goal state after:
Module: Mathlib.LinearAlgebra.Matrix.SchurComplement

Goal state before:
pp: m : Type u_2
n : Type u_3
α : Type u_4
inst✝⁵ : Fintype m
inst✝⁴ : Fintype n
inst✝³ : DecidableEq m
inst✝² : DecidableEq n
inst✝¹ : CommRing α
A : Matrix m m α
B : Matrix m n α
C : Matrix n m α
D : Matrix n n α
inst✝ : Invertible A
⊢ 1 * 1 * (A.det * (D - C * ⅟A * B).det) * (1 * 1) = A.det * (D - C * ⅟A * B).det

Tactic:
one_mul,

Goal state after:
m : Type u_2
n : Type u_3
α : Type u_4
inst✝⁵ : Fintype m
inst✝⁴ : Fintype n
inst✝³ : DecidableEq m
inst✝² : DecidableEq n
inst✝¹ : CommRing α
A : Matrix m m α
B : Matrix m n α
C : Matrix n m α
D : Matrix n n α
inst✝ : Invertible A
⊢ 1 * (A.det * (D - C * ⅟A * B).det) * 1 = A.det * (D - C * ⅟A * B).det
Module: Mathlib.LinearAlgebra.Matrix.SchurComplement

Goal state before:
pp: m : Type u_2
n : Type u_3
α : Type u_4
inst✝⁵ : Fintype m
inst✝⁴ : Fintype n
inst✝³ : DecidableEq m
inst✝² : DecidableEq n
inst✝¹ : CommRing α
A : Matrix m m α
B : Matrix m n α
C : Matrix n m α
D : Matrix n n α
inst✝ : Invertible A
⊢ 1 * (A.det * (D - C * ⅟A * B).det) * 1 = A.det * (D - C * ⅟A * B).det

Tactic:
one_mul,

Goal state after:
m : Type u_2
n : Type u_3
α : Type u_4
inst✝⁵ : Fintype m
inst✝⁴ : Fintype n
inst✝³ : DecidableEq m
inst✝² : DecidableEq n
inst✝¹ : CommRing α
A : Matrix m m α
B : Matrix m n α
C : Matrix n m α
D : Matrix n n α
inst✝ : Invertible A
⊢ A.det * (D - C * ⅟A * B).det * 1 = A.det * (D - C * ⅟A * B).det
Module: Mathlib.RingTheory.Nilpotent.Basic

Goal state before:
pp: R : Type u_1
x y : R
inst✝ : Semiring R
h_comm : Commute x y
m n k : ℕ
hx : x ^ m = 0
hy : y ^ n = 0
h : m + n ≤ k + 1
⊢ ∑ m ∈ Finset.antidiagonal k, k.choose m.1 • (x ^ m.1 * y ^ m.2) = 0

Tactic:
apply Finset.sum_eq_zero

Goal state after:
R : Type u_1
x y : R
inst✝ : Semiring R
h_comm : Commute x y
m n k : ℕ
hx : x ^ m = 0
hy : y ^ n = 0
h : m + n ≤ k + 1
⊢ ∀ x_1 ∈ Finset.antidiagonal k, k.choose x_1.1 • (x ^ x_1.1 * y ^ x_1.2) = 0
Module: Mathlib.Algebra.Module.SpanRank

Goal state before:
pp: case neg
R : Type u_1
M : Type u
inst✝² : Semiring R
inst✝¹ : AddCommMonoid M
inst✝ : Module R M
p : Submodule R M
h2 : ⨅ s, ⨅ (_ : span R s = p), s.encard ≠ ⊤
s : Set M
h : span R s = p
hs : ¬s.Finite
⊢ ⨅ s, (↑↑s).encard ≤ s.encard

Tactic:
· rw [Set.Infinite.encard_eq hs]
        exact OrderTop.le_top _

Goal state after:
Module: Mathlib.Algebra.Module.SpanRank

Goal state before:
pp: R : Type u_1
M : Type u
inst✝² : Semiring R
inst✝¹ : AddCommMonoid M
inst✝ : Module R M
s : Set M
hs : s.Finite
⊢ ↑(span R s).spanFinrank ≤ ↑s.ncard

Tactic:
exact le_trans (spanFinrank_span_le_encard _) hs.cast_ncard_eq.ge

Goal state after:
Module: Mathlib.Algebra.Module.SpanRank

Goal state before:
pp: R : Type u
inst✝¹ : Semiring R
T : Type v
inst✝ : Semiring T
f : R →+* T
I : Ideal R
r : R
hr : r ∈ I
⊢ f r ∈ map f I

Tactic:
exact mem_map_of_mem f hr

Goal state after:
Module: Mathlib.RingTheory.IntegralClosure.IsIntegral.Basic

Goal state before:
pp: case refine_2
R : Type u_6
A : Type u_7
inst✝² : CommRing R
inst✝¹ : Semiring A
inst✝ : Algebra R A
x : A
f : R[X]
hf : f.Monic
hfx : (aeval x) f = 0
a✝ : Nontrivial A
hf1 : f ≠ 1
p : R[X]
hr : (aeval x) p ∈ (aeval x).range
⊢ (aeval x) p ∈ span R ↑(Finset.image (fun x_1 ↦ x ^ x_1) (Finset.range f.natDegree))

Tactic:
rw [← modByMonic_add_div p f, map_add, map_mul, hfx,
      zero_mul, add_zero, ← sum_C_mul_X_pow_eq (p %ₘ f), aeval_def, eval₂_sum, sum_def]

Goal state after:
case refine_2
R : Type u_6
A : Type u_7
inst✝² : CommRing R
inst✝¹ : Semiring A
inst✝ : Algebra R A
x : A
f : R[X]
hf : f.Monic
hfx : (aeval x) f = 0
a✝ : Nontrivial A
hf1 : f ≠ 1
p : R[X]
hr : (aeval x) p ∈ (aeval x).range
⊢ ∑ n ∈ (p %ₘ f).support, eval₂ (algebraMap R A) x (C ((p %ₘ f).coeff n) * X ^ n) ∈
    span R ↑(Finset.image (fun x_1 ↦ x ^ x_1) (Finset.range f.natDegree))
Module: Mathlib.LinearAlgebra.Matrix.Charpoly.Coeff

Goal state before:
pp: case neg
R : Type u
inst✝³ : CommRing R
n : Type v
inst✝² : DecidableEq n
inst✝¹ : Fintype n
M : Matrix n n R
inst✝ : Nontrivial R
hn : Fintype.card n = 2
this : Nonempty n
i : ℕ
hi : i ∉ range 3
⊢ M.charpoly.coeff i = (X ^ 2 - C M.trace * X + C M.det).coeff i

Tactic:
rw [Finset.mem_range, not_lt, Nat.succ_le_iff] at hi

Goal state after:
case neg
R : Type u
inst✝³ : CommRing R
n : Type v
inst✝² : DecidableEq n
inst✝¹ : Fintype n
M : Matrix n n R
inst✝ : Nontrivial R
hn : Fintype.card n = 2
this : Nonempty n
i : ℕ
hi : 2 < i
⊢ M.charpoly.coeff i = (X ^ 2 - C M.trace * X + C M.det).coeff i
Module: Mathlib.Data.Nat.Choose.Cast

Goal state before:
pp: K : Type u_1
inst✝¹ : DivisionRing K
inst✝ : NeZero 2
a : ℕ
⊢ ↑(a.choose 2) = ↑(2 * a.choose 2) / 2

Tactic:
mul_comm,

Goal state after:
K : Type u_1
inst✝¹ : DivisionRing K
inst✝ : NeZero 2
a : ℕ
⊢ ↑(a.choose 2) = ↑(a.choose 2 * 2) / 2
Module: Mathlib.LinearAlgebra.Matrix.Charpoly.Coeff

Goal state before:
pp: case zero
R : Type u
inst✝² : CommRing R
n : Type v
inst✝¹ : DecidableEq n
inst✝ : Fintype n
M : Matrix n n R
I : Ideal R
h : ∀ (i j : n), M i j ∈ I
k : ℕ
c : Equiv.Perm n
this : ∑ x, 1 = Fintype.card n
i : n
⊢ 0 - M (c i) i ∈ I

Tactic:
zero_sub,

Goal state after:
case zero
R : Type u
inst✝² : CommRing R
n : Type v
inst✝¹ : DecidableEq n
inst✝ : Fintype n
M : Matrix n n R
I : Ideal R
h : ∀ (i j : n), M i j ∈ I
k : ℕ
c : Equiv.Perm n
this : ∑ x, 1 = Fintype.card n
i : n
⊢ -M (c i) i ∈ I
Module: Mathlib.LinearAlgebra.Matrix.Charpoly.Coeff

Goal state before:
pp: R : Type u
inst✝² : CommRing R
n : Type v
inst✝¹ : DecidableEq n
inst✝ : Fintype n
M : Matrix n n R
a✝ : Nontrivial R
t : R[T;T⁻¹] := T 1
t_inv : R[T;T⁻¹] := T (-1)
p : R[T;T⁻¹] := ((scalar n) t - M.map ⇑LaurentPolynomial.C).det
q : R[T;T⁻¹] := (1 - (scalar n) t * M.map ⇑LaurentPolynomial.C).det
ht : t_inv * t = 1
hp : toLaurentAlg M.charpoly = p
hq : toLaurentAlg M.charpolyRev = q
⊢ t_inv ^ Fintype.card n * p = invert q

Tactic:
rw [← det_smul, smul_sub, scalar_apply, ← diagonal_smul, Pi.smul_def, smul_eq_mul, ht,
    diagonal_one, invert.map_det]

Goal state after:
R : Type u
inst✝² : CommRing R
n : Type v
inst✝¹ : DecidableEq n
inst✝ : Fintype n
M : Matrix n n R
a✝ : Nontrivial R
t : R[T;T⁻¹] := T 1
t_inv : R[T;T⁻¹] := T (-1)
p : R[T;T⁻¹] := ((scalar n) t - M.map ⇑LaurentPolynomial.C).det
q : R[T;T⁻¹] := (1 - (scalar n) t * M.map ⇑LaurentPolynomial.C).det
ht : t_inv * t = 1
hp : toLaurentAlg M.charpoly = p
hq : toLaurentAlg M.charpolyRev = q
⊢ (1 - t_inv • M.map ⇑LaurentPolynomial.C).det = (invert.mapMatrix (1 - (scalar n) t * M.map ⇑LaurentPolynomial.C)).det
Module: Mathlib.Algebra.Polynomial.HasseDeriv

Goal state before:
pp: R : Type u_1
inst✝ : Semiring R
f : R[X]
this : ((hasseDeriv f.natDegree) f).natDegree ≤ 0
⊢ C (1 * f.coeff f.natDegree) = C f.leadingCoeff

Tactic:
one_mul,

Goal state after:
R : Type u_1
inst✝ : Semiring R
f : R[X]
this : ((hasseDeriv f.natDegree) f).natDegree ≤ 0
⊢ C (f.coeff f.natDegree) = C f.leadingCoeff
Module: Mathlib.RingTheory.Polynomial.ScaleRoots

Goal state before:
pp: case e'_6
S : Type u_2
K : Type u_4
inst✝¹ : Semiring S
inst✝ : Field K
p : S[X]
f : S →+* K
hf : Function.Injective ⇑f
r s : S
hr : eval₂ f (f r / f s) p = 0
hs : s ∈ nonZeroDivisors S
a✝ : Nontrivial S
⊢ f r = f s * f r / f s

Tactic:
mul_comm,

Goal state after:
case e'_6
S : Type u_2
K : Type u_4
inst✝¹ : Semiring S
inst✝ : Field K
p : S[X]
f : S →+* K
hf : Function.Injective ⇑f
r s : S
hr : eval₂ f (f r / f s) p = 0
hs : s ∈ nonZeroDivisors S
a✝ : Nontrivial S
⊢ f r = f r * f s / f s
Module: Mathlib.RingTheory.Polynomial.ScaleRoots

Goal state before:
pp: case inr
R : Type u_1
inst✝ : CommSemiring R
p q : R[X]
r : R
n : ℕ
h : n ≤ (p * q).natDegree
⊢ r ^ (p.natDegree + q.natDegree - (p * q).natDegree) * ((p * q).coeff n * r ^ ((p * q).natDegree - n)) =
    (p * q).coeff n * r ^ (p.natDegree + q.natDegree - n)

Tactic:
mul_comm,

Goal state after:
case inr
R : Type u_1
inst✝ : CommSemiring R
p q : R[X]
r : R
n : ℕ
h : n ≤ (p * q).natDegree
⊢ (p * q).coeff n * r ^ ((p * q).natDegree - n) * r ^ (p.natDegree + q.natDegree - (p * q).natDegree) =
    (p * q).coeff n * r ^ (p.natDegree + q.natDegree - n)
Module: Mathlib.RingTheory.Polynomial.IntegralNormalization

Goal state before:
pp: case pos
R : Type u
inst✝ : Semiring R
p : R[X]
i : ℕ
h : ¬p.degree = ↑i
h' : ↑i < p.degree
⊢ p.coeff i * p.leadingCoeff ^ (p.natDegree - 1 - i) * p.leadingCoeff = p.coeff i * p.leadingCoeff ^ (p.natDegree - i)

Tactic:
rw [mul_assoc, ← pow_succ, tsub_right_comm, tsub_add_cancel_of_le]
      rw [le_tsub_iff_left (coe_lt_degree.mp h').le, Nat.succ_le_iff]
      exact coe_lt_degree.mp h'

Goal state after:
Module: Mathlib.RingTheory.Polynomial.IntegralNormalization

Goal state before:
pp: S : Type v
inst✝ : CommSemiring S
p : S[X]
⊢ C p.leadingCoeff * p.integralNormalization = p.scaleRoots p.leadingCoeff

Tactic:
mul_comm,

Goal state after:
S : Type v
inst✝ : CommSemiring S
p : S[X]
⊢ p.integralNormalization * C p.leadingCoeff = p.scaleRoots p.leadingCoeff
Module: Mathlib.RingTheory.Polynomial.ScaleRoots

Goal state before:
pp: R : Type u_1
inst✝ : CommSemiring R
p q : R[X]
r : R
h : p.natDegree = q.natDegree
n : ℕ
x✝ : (p + q).natDegree < n ∨ n ≤ (p + q).natDegree
⊢ (p.coeff n + q.coeff n) * r ^ ((p + q).natDegree - n + (p.natDegree - (p + q).natDegree)) =
    (p.coeff n + q.coeff n) * r ^ (p.natDegree - n)

Tactic:
cases lt_or_ge (natDegree (p + q)) n with

Goal state after:
Module: Mathlib.Algebra.Polynomial.Splits

Goal state before:
pp: R : Type u_1
inst✝ : Semiring R
n : ℕ
a : R
⊢ ((Polynomial.monomial n) a).Splits

Tactic:
simp [← C_mul_X_pow_eq_monomial]

Goal state after:
Module: Mathlib.RingTheory.Polynomial.ScaleRoots

Goal state before:
pp: case inr.inr
R : Type u_1
inst✝ : CommRing R
p : R[X]
r a : R
hr : IsLeftRegular r
h✝ : Nontrivial R
hp : p ≠ 0
q : R[X]
e : p = (X - C a) ^ rootMultiplicity a p * q
hq : ¬X - C a ∣ q
hq0 : q ≠ 0
⊢ rootMultiplicity (r * a) ((X - C (a * r)) ^ rootMultiplicity a p * q.scaleRoots r) = rootMultiplicity a p

pp: case inr.inr.hp
R : Type u_1
inst✝ : CommRing R
p : R[X]
r a : R
hr : IsLeftRegular r
h✝ : Nontrivial R
hp : p ≠ 0
q : R[X]
e : p = (X - C a) ^ rootMultiplicity a p * q
hq : ¬X - C a ∣ q
hq0 : q ≠ 0
⊢ (X - C a).leadingCoeff ^ rootMultiplicity a p ≠ 0

pp: case inr.inr.h
R : Type u_1
inst✝ : CommRing R
p : R[X]
r a : R
hr : IsLeftRegular r
h✝ : Nontrivial R
hp : p ≠ 0
q : R[X]
e : p = (X - C a) ^ rootMultiplicity a p * q
hq : ¬X - C a ∣ q
hq0 : q ≠ 0
⊢ ((X - C a) ^ rootMultiplicity a p).leadingCoeff * q.leadingCoeff ≠ 0

Tactic:
mul_comm,

Goal state after:
case inr.inr
R : Type u_1
inst✝ : CommRing R
p : R[X]
r a : R
hr : IsLeftRegular r
h✝ : Nontrivial R
hp : p ≠ 0
q : R[X]
e : p = (X - C a) ^ rootMultiplicity a p * q
hq : ¬X - C a ∣ q
hq0 : q ≠ 0
⊢ rootMultiplicity (a * r) ((X - C (a * r)) ^ rootMultiplicity a p * q.scaleRoots r) = rootMultiplicity a p

case inr.inr.hp
R : Type u_1
inst✝ : CommRing R
p : R[X]
r a : R
hr : IsLeftRegular r
h✝ : Nontrivial R
hp : p ≠ 0
q : R[X]
e : p = (X - C a) ^ rootMultiplicity a p * q
hq : ¬X - C a ∣ q
hq0 : q ≠ 0
⊢ (X - C a).leadingCoeff ^ rootMultiplicity a p ≠ 0

case inr.inr.h
R : Type u_1
inst✝ : CommRing R
p : R[X]
r a : R
hr : IsLeftRegular r
h✝ : Nontrivial R
hp : p ≠ 0
q : R[X]
e : p = (X - C a) ^ rootMultiplicity a p * q
hq : ¬X - C a ∣ q
hq0 : q ≠ 0
⊢ ((X - C a) ^ rootMultiplicity a p).leadingCoeff * q.leadingCoeff ≠ 0
Module: Mathlib.RingTheory.Polynomial.ScaleRoots

Goal state before:
pp: case inr.inr
R : Type u_1
inst✝ : CommRing R
p : R[X]
r a : R
hr : IsLeftRegular r
h✝ : Nontrivial R
hp : p ≠ 0
q : R[X]
e : p = (X - C a) ^ rootMultiplicity a p * q
hq : ¬eval a q = 0
hq0 : q ≠ 0
⊢ eval (a * r) (q.scaleRoots r) = 0 → q.scaleRoots r = 0

Tactic:
mul_comm,

Goal state after:
case inr.inr
R : Type u_1
inst✝ : CommRing R
p : R[X]
r a : R
hr : IsLeftRegular r
h✝ : Nontrivial R
hp : p ≠ 0
q : R[X]
e : p = (X - C a) ^ rootMultiplicity a p * q
hq : ¬eval a q = 0
hq0 : q ≠ 0
⊢ eval (r * a) (q.scaleRoots r) = 0 → q.scaleRoots r = 0
Module: Mathlib.RingTheory.Polynomial.ScaleRoots

Goal state before:
pp: case inr.inr.h
R : Type u_1
inst✝ : CommRing R
p : R[X]
r a : R
hr : IsLeftRegular r
h✝ : Nontrivial R
hp : p ≠ 0
q : R[X]
e : p = (X - C a) ^ rootMultiplicity a p * q
hq : ¬X - C a ∣ q
hq0 : q ≠ 0
⊢ 1 * q.leadingCoeff ≠ 0

Tactic:
one_mul,

Goal state after:
case inr.inr.h
R : Type u_1
inst✝ : CommRing R
p : R[X]
r a : R
hr : IsLeftRegular r
h✝ : Nontrivial R
hp : p ≠ 0
q : R[X]
e : p = (X - C a) ^ rootMultiplicity a p * q
hq : ¬X - C a ∣ q
hq0 : q ≠ 0
⊢ q.leadingCoeff ≠ 0
Module: Mathlib.Algebra.Polynomial.Splits

Goal state before:
pp: case refine_2
R : Type u_1
inst✝ : CommSemiring R
f : R[X]
⊢ (∃ m, f = C f.leadingCoeff * (Multiset.map (fun x ↦ X + C x) m).prod) → f.Splits

Tactic:
rintro ⟨m, hm⟩
    exact hm ▸ (Splits.C _).mul (.multisetProd (by simp [Splits.X_add_C]))

Goal state after:
Module: Mathlib.Algebra.Polynomial.Splits

Goal state before:
pp: case neg
R : Type u_1
inst✝¹ : CommRing R
f : R[X]
inst✝ : IsDomain R
a : R
hf : ((X - C a) * f).Splits
hf₀ : ¬f = 0
this : (X - C a) * f = C (1 * f.leadingCoeff) * (Multiset.map (fun x ↦ X - C x) ((X - C a) * f).roots).prod
⊢ f.Splits

Tactic:
one_mul,

Goal state after:
case neg
R : Type u_1
inst✝¹ : CommRing R
f : R[X]
inst✝ : IsDomain R
a : R
hf : ((X - C a) * f).Splits
hf₀ : ¬f = 0
this : (X - C a) * f = C f.leadingCoeff * (Multiset.map (fun x ↦ X - C x) ((X - C a) * f).roots).prod
⊢ f.Splits
Module: Mathlib.Algebra.Polynomial.Splits

Goal state before:
pp: R : Type u_1
inst✝¹ : CommRing R
inst✝ : IsDomain R
n : ℕ
ih : ∀ {f g : R[X]}, f ≠ 0 → g ≠ 0 → ∀ (p : R[X]), f * g = p → p.Splits → p.natDegree = n → f.Splits ∧ g.Splits
f g : R[X]
hf₀ : f ≠ 0
hg₀ : g ≠ 0
p : R[X]
hp : f * g = p
h : p.Splits
hn : p.natDegree = n + 1
a : R
ha : eval a p = 0
this : X - C a ∣ f ∨ X - C a ∣ g
hf : X - C a ∣ f
⊢ f.Splits ∧ g.Splits

Tactic:
obtain ⟨f, rfl⟩ := hf

Goal state after:
R : Type u_1
inst✝¹ : CommRing R
inst✝ : IsDomain R
n : ℕ
ih : ∀ {f g : R[X]}, f ≠ 0 → g ≠ 0 → ∀ (p : R[X]), f * g = p → p.Splits → p.natDegree = n → f.Splits ∧ g.Splits
g : R[X]
hg₀ : g ≠ 0
p : R[X]
h : p.Splits
hn : p.natDegree = n + 1
a : R
ha : eval a p = 0
f : R[X]
hf₀ : (X - C a) * f ≠ 0
hp : (X - C a) * f * g = p
this : X - C a ∣ (X - C a) * f ∨ X - C a ∣ g
⊢ ((X - C a) * f).Splits ∧ g.Splits
Module: Mathlib.Algebra.Polynomial.Splits

Goal state before:
pp: R : Type u_1
inst✝ : Field R
f g : R[X]
hg : g.natDegree = 1
hf : (f.comp g).Splits
⊢ f.Splits

Tactic:
obtain ⟨a, b, rfl⟩ := exists_eq_X_add_C_of_natDegree_le_one hg.le

Goal state after:
R : Type u_1
inst✝ : Field R
f : R[X]
a b : R
hg : (C a * X + C b).natDegree = 1
hf : (f.comp (C a * X + C b)).Splits
⊢ f.Splits
Module: Mathlib.Algebra.Polynomial.Splits

Goal state before:
pp: R : Type u_1
inst✝ : Field R
f : R[X]
a b : R
hg : (C a * X + C b).natDegree = 1
hf : (f.comp (C a * X + C b)).Splits
ha : a ≠ 0
⊢ f = f.comp (1 * (X - C b) + C b)

Tactic:
one_mul,

Goal state after:
R : Type u_1
inst✝ : Field R
f : R[X]
a b : R
hg : (C a * X + C b).natDegree = 1
hf : (f.comp (C a * X + C b)).Splits
ha : a ≠ 0
⊢ f = f.comp (X - C b + C b)
Module: Mathlib.RingTheory.Localization.Integral

Goal state before:
pp: case neg
R : Type u_1
inst✝³ : CommRing R
M : Submonoid R
Rₘ : Type u_3
inst✝² : CommRing Rₘ
inst✝¹ : Algebra R Rₘ
inst✝ : IsLocalization M Rₘ
p : Rₘ[X]
hp : p.leadingCoeff ∈ (algebraMap R Rₘ).range
n : ℕ
h₁ : n ∈ p.support
h₂ : ¬n = p.natDegree
this : n + 1 ≤ p.natDegree
⊢ p.coeff n *
      ((algebraMap R Rₘ) ↑(commonDenom M p.support p.coeff) ^ (p.natDegree - n - 1) *
        (algebraMap R Rₘ) ↑(commonDenom M p.support p.coeff)) ∈
    Set.range ⇑(algebraMap R Rₘ)

Tactic:
mul_comm,

Goal state after:
case neg
R : Type u_1
inst✝³ : CommRing R
M : Submonoid R
Rₘ : Type u_3
inst✝² : CommRing Rₘ
inst✝¹ : Algebra R Rₘ
inst✝ : IsLocalization M Rₘ
p : Rₘ[X]
hp : p.leadingCoeff ∈ (algebraMap R Rₘ).range
n : ℕ
h₁ : n ∈ p.support
h₂ : ¬n = p.natDegree
this : n + 1 ≤ p.natDegree
⊢ (algebraMap R Rₘ) ↑(commonDenom M p.support p.coeff) ^ (p.natDegree - n - 1) *
        (algebraMap R Rₘ) ↑(commonDenom M p.support p.coeff) *
      p.coeff n ∈
    Set.range ⇑(algebraMap R Rₘ)
Module: Mathlib.RingTheory.Localization.Integral

Goal state before:
pp: case inr.refine_3
R : Type u_1
inst✝⁷ : CommRing R
M : Submonoid R
S : Type u_2
inst✝⁶ : CommRing S
inst✝⁵ : Algebra R S
Rₘ : Type u_3
inst✝⁴ : CommRing Rₘ
inst✝³ : Algebra R Rₘ
inst✝² : IsLocalization M Rₘ
inst✝¹ : Algebra Rₘ S
inst✝ : IsScalarTower R Rₘ S
x : S
nontriv : Nontrivial Rₘ
p : Rₘ[X]
hp₁ : p.Monic
hp₂ : eval₂ (algebraMap Rₘ S) x p = 0
p' : R[X]
hp'₁ : Polynomial.map (algebraMap R Rₘ) p' = p.scaleRoots ((algebraMap R Rₘ) ↑(commonDenom M p.support p.coeff))
hp'₂ : p'.Monic
⊢ eval₂ (algebraMap R S) (commonDenom M p.support p.coeff • x) p' = 0

Tactic:
rw [IsScalarTower.algebraMap_eq R Rₘ S, ← Polynomial.eval₂_map, hp'₁, Submonoid.smul_def,
      Algebra.smul_def, IsScalarTower.algebraMap_apply R Rₘ S]

Goal state after:
case inr.refine_3
R : Type u_1
inst✝⁷ : CommRing R
M : Submonoid R
S : Type u_2
inst✝⁶ : CommRing S
inst✝⁵ : Algebra R S
Rₘ : Type u_3
inst✝⁴ : CommRing Rₘ
inst✝³ : Algebra R Rₘ
inst✝² : IsLocalization M Rₘ
inst✝¹ : Algebra Rₘ S
inst✝ : IsScalarTower R Rₘ S
x : S
nontriv : Nontrivial Rₘ
p : Rₘ[X]
hp₁ : p.Monic
hp₂ : eval₂ (algebraMap Rₘ S) x p = 0
p' : R[X]
hp'₁ : Polynomial.map (algebraMap R Rₘ) p' = p.scaleRoots ((algebraMap R Rₘ) ↑(commonDenom M p.support p.coeff))
hp'₂ : p'.Monic
⊢ eval₂ (algebraMap Rₘ S) ((algebraMap Rₘ S) ((algebraMap R Rₘ) ↑(commonDenom M p.support p.coeff)) * x)
      (p.scaleRoots ((algebraMap R Rₘ) ↑(commonDenom M p.support p.coeff))) =
    0
Module: Mathlib.RingTheory.Flat.FaithfullyFlat.Basic

Goal state before:
pp: R : Type u
M : Type v
inst✝⁵ : CommRing R
inst✝⁴ : AddCommGroup M
inst✝³ : Module R M
N : Type u_1
inst✝² : AddCommGroup N
inst✝¹ : Module R N
inst✝ : FaithfullyFlat R N
⊢ Nontrivial (M ⊗[R] N) ↔ Nontrivial M

Tactic:
contrapose!; exact subsingleton_tensorProduct_iff_left R M

Goal state after:
Module: Mathlib.RingTheory.Algebraic.Integral

Goal state before:
pp: R : Type u_1
A : Type u_3
inst✝² : CommRing R
inst✝¹ : Ring A
inst✝ : Algebra R A
z : A
y : R
hy : ¬IsNilpotent y
h✝ : IsIntegral R (y • z)
p : R[X]
monic : p.Monic
eval0 : eval₂ (algebraMap R A) (y • z) p = 0
h : p.leadingCoeff * (C y * X).leadingCoeff ^ p.natDegree = 0
hy0 : y ≠ 0
⊢ False

pp: R : Type u_1
A : Type u_3
inst✝² : CommRing R
inst✝¹ : Ring A
inst✝ : Algebra R A
z : A
y : R
hy : ¬IsNilpotent y
h✝ : IsIntegral R (y • z)
p : R[X]
monic : p.Monic
eval0 : eval₂ (algebraMap R A) (y • z) p = 0
h : (p.comp (C y * X)).coeff (p.natDegree * (C y * X).natDegree) = 0
hy0 : y ≠ 0
⊢ (C y * X).natDegree ≠ 0

Tactic:
monic,

Goal state after:
R : Type u_1
A : Type u_3
inst✝² : CommRing R
inst✝¹ : Ring A
inst✝ : Algebra R A
z : A
y : R
hy : ¬IsNilpotent y
h✝ : IsIntegral R (y • z)
p : R[X]
monic : p.Monic
eval0 : eval₂ (algebraMap R A) (y • z) p = 0
h : 1 * (C y * X).leadingCoeff ^ p.natDegree = 0
hy0 : y ≠ 0
⊢ False

R : Type u_1
A : Type u_3
inst✝² : CommRing R
inst✝¹ : Ring A
inst✝ : Algebra R A
z : A
y : R
hy : ¬IsNilpotent y
h✝ : IsIntegral R (y • z)
p : R[X]
monic : p.Monic
eval0 : eval₂ (algebraMap R A) (y • z) p = 0
h : (p.comp (C y * X)).coeff (p.natDegree * (C y * X).natDegree) = 0
hy0 : y ≠ 0
⊢ (C y * X).natDegree ≠ 0