Split polynomials

A polynomial f : K[X] splits over a field extension L of K if it is zero or all of its irreducible factors over L have degree 1.

Main definitions

• Polynomial.Splits i f: A predicate on a homomorphism i : K →+* L from a commutative ring to a field and a polynomial f saying that f.map i factors in L.

@[deprecated Polynomial.Splits.zero (since := "2025-11-24")]

theorem Polynomial.splits_zero {R : Type u_1} [Semiring R] : Splits 0

Alias of Polynomial.Splits.zero.

@[deprecated "Use `Splits.C` instead." (since := "2025-11-24")]

theorem Polynomial.splits_of_map_eq_C {K : Type v} {L : Type w} [CommRing K] [Field L] (i : K →+* L) {f : Polynomial K} {a : L} (h : map i f = C a) : (map i f).Splits

@[deprecated Polynomial.Splits.C (since := "2025-11-24")]

theorem Polynomial.splits_C {R : Type u_1} [Semiring R] (a : R) : (C a).Splits

Alias of Polynomial.Splits.C.

@[deprecated Polynomial.Splits.of_degree_eq_one (since := "2025-11-24")]

theorem Polynomial.splits_of_map_degree_eq_one {R : Type u_1} [DivisionSemiring R] {f : Polynomial R} (hf : f.degree = 1) : f.Splits

Alias of Polynomial.Splits.of_degree_eq_one.

@[deprecated Polynomial.Splits.of_degree_le_one (since := "2025-11-24")]

theorem Polynomial.splits_of_degree_le_one {R : Type u_1} [DivisionSemiring R] {f : Polynomial R} (hf : f.degree ≤ 1) : f.Splits

Alias of Polynomial.Splits.of_degree_le_one.

@[deprecated Polynomial.Splits.of_degree_eq_one (since := "2025-11-24")]

theorem Polynomial.splits_of_degree_eq_one {R : Type u_1} [DivisionSemiring R] {f : Polynomial R} (hf : f.degree = 1) : f.Splits

Alias of Polynomial.Splits.of_degree_eq_one.

@[deprecated Polynomial.Splits.of_natDegree_le_one (since := "2025-11-24")]

theorem Polynomial.splits_of_natDegree_le_one {R : Type u_1} [DivisionSemiring R] {f : Polynomial R} (hf : f.natDegree ≤ 1) : f.Splits

Alias of Polynomial.Splits.of_natDegree_le_one.

@[deprecated Polynomial.Splits.of_natDegree_eq_one (since := "2025-11-24")]

theorem Polynomial.splits_of_natDegree_eq_one {R : Type u_1} [DivisionSemiring R] {f : Polynomial R} (hf : f.natDegree = 1) : f.Splits

Alias of Polynomial.Splits.of_natDegree_eq_one.

@[deprecated Polynomial.Splits.mul (since := "2025-11-25")]

theorem Polynomial.splits_mul {R : Type u_1} [Semiring R] {f g : Polynomial R} (hf : f.Splits) (hg : g.Splits) : (f * g).Splits

Alias of Polynomial.Splits.mul.

@[deprecated Polynomial.splits_mul_iff (since := "2025-11-25")]

theorem Polynomial.splits_of_splits_mul' {R : Type u_1} [CommRing R] {f g : Polynomial R} [IsDomain R] (hf₀ : f ≠ 0) (hg₀ : g ≠ 0) : (f * g).Splits ↔ f.Splits ∧ g.Splits

Alias of Polynomial.splits_mul_iff.

@[deprecated "Use `Polynomial.map_map` instead." (since := "2025-11-24")]

theorem Polynomial.splits_map_iff {F : Type u} {K : Type v} [CommRing K] [Field F] {L : Type u_2} [CommRing L] (i : K →+* L) (j : L →+* F) {f : Polynomial K} : (map j (map i f)).Splits ↔ (map (j.comp i) f).Splits

@[deprecated Polynomial.Splits.one (since := "2025-11-24")]

theorem Polynomial.splits_one {R : Type u_1} [Semiring R] : Splits 1

Alias of Polynomial.Splits.one.

@[deprecated Polynomial.Splits.X_sub_C (since := "2025-11-24")]

theorem Polynomial.splits_X_sub_C {R : Type u_1} [Ring R] (a : R) : (X - C a).Splits

Alias of Polynomial.Splits.X_sub_C.

@[deprecated Polynomial.Splits.X (since := "2025-11-24")]

theorem Polynomial.splits_X {R : Type u_1} [Semiring R] : X.Splits

Alias of Polynomial.Splits.X.

@[deprecated Polynomial.Splits.prod (since := "2025-11-24")]

theorem Polynomial.splits_prod {R : Type u_1} [CommSemiring R] {ι : Type u_2} {f : ι → Polynomial R} {s : Finset ι} (h : ∀ i ∈ s, (f i).Splits) : (∏ i ∈ s, f i).Splits

Alias of Polynomial.Splits.prod.

@[deprecated Polynomial.Splits.pow (since := "2025-11-24")]

theorem Polynomial.splits_pow {R : Type u_1} [Semiring R] {f : Polynomial R} (hf : f.Splits) (n : ℕ) : (f ^ n).Splits

Alias of Polynomial.Splits.pow.

@[deprecated Polynomial.Splits.X_pow (since := "2025-11-24")]

theorem Polynomial.splits_X_pow {R : Type u_1} [Semiring R] (n : ℕ) : (X ^ n).Splits

Alias of Polynomial.Splits.X_pow.

@[deprecated "Use `Polynomial.map_id` instead." (since := "2025-11-24")]

theorem Polynomial.splits_id_iff_splits {K : Type v} {L : Type w} [CommRing K] [Field L] (i : K →+* L) {f : Polynomial K} : (map (RingHom.id L) (map i f)).Splits ↔ (map i f).Splits

@[deprecated Polynomial.Splits.comp_of_degree_le_one (since := "2025-11-25")]

theorem Polynomial.Splits.comp_of_map_degree_le_one {R : Type u_1} [Field R] {f g : Polynomial R} (hf : f.Splits) (hg : g.degree ≤ 1) : (f.comp g).Splits

Alias of Polynomial.Splits.comp_of_degree_le_one.

theorem Polynomial.exists_root_of_splits' {K : Type v} {L : Type w} [CommRing K] [Field L] (i : K →+* L) {f : Polynomial K} (hs : (map i f).Splits) (hf0 : (map i f).degree ≠ 0) : ∃ (x : L), eval₂ i x f = 0

theorem Polynomial.roots_ne_zero_of_splits' {K : Type v} {L : Type w} [CommRing K] [Field L] (i : K →+* L) {f : Polynomial K} (hs : (map i f).Splits) (hf0 : (map i f).natDegree ≠ 0) : (map i f).roots ≠ 0

def Polynomial.rootOfSplits' {K : Type v} {L : Type w} [CommRing K] [Field L] (i : K →+* L) {f : Polynomial K} (hf : (map i f).Splits) (hfd : (map i f).degree ≠ 0) : L

Pick a root of a polynomial that splits. See rootOfSplits for polynomials over a field which has simpler assumptions.

Equations

• Polynomial.rootOfSplits' i hf hfd = Classical.choose ⋯

theorem Polynomial.map_rootOfSplits' {K : Type v} {L : Type w} [CommRing K] [Field L] (i : K →+* L) {f : Polynomial K} (hf : (map i f).Splits) (hfd : (map i f).degree ≠ 0) : eval₂ i (rootOfSplits' i hf hfd) f = 0

theorem Polynomial.natDegree_eq_card_roots' {K : Type v} {L : Type w} [CommRing K] [Field L] {p : Polynomial K} {i : K →+* L} (hsplit : (map i p).Splits) : (map i p).natDegree = (map i p).roots.card

theorem Polynomial.degree_eq_card_roots' {K : Type v} {L : Type w} [CommRing K] [Field L] {p : Polynomial K} {i : K →+* L} (p_ne_zero : map i p ≠ 0) (hsplit : (map i p).Splits) : (map i p).degree = ↑(map i p).roots.card

theorem Polynomial.aeval_root_of_mapAlg_eq_multiset_prod_X_sub_C {R : Type u_1} {L : Type w} [CommSemiring R] [CommRing L] [Algebra R L] (s : Multiset L) {x : L} (hx : x ∈ s) {p : Polynomial R} (hp : (mapAlg R L) p = (Multiset.map (fun (a : L) => X - C a) s).prod) : (aeval x) p = 0

theorem Polynomial.splits_iff {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) (f : Polynomial K) : (map i f).Splits ↔ f = 0 ∨ ∀ {g : Polynomial L}, Irreducible g → g ∣ map i f → g.degree = 1

This lemma is for polynomials over a field.

theorem Polynomial.Splits.def {K : Type v} {L : Type w} [Field K] [Field L] {i : K →+* L} {f : Polynomial K} (h : (map i f).Splits) : f = 0 ∨ ∀ {g : Polynomial L}, Irreducible g → g ∣ map i f → g.degree = 1

This lemma is for polynomials over a field.

@[deprecated Polynomial.splits_mul_iff (since := "2025-11-25")]

theorem Polynomial.splits_of_splits_mul {R : Type u_1} [CommRing R] {f g : Polynomial R} [IsDomain R] (hf₀ : f ≠ 0) (hg₀ : g ≠ 0) : (f * g).Splits ↔ f.Splits ∧ g.Splits

Alias of Polynomial.splits_mul_iff.

@[deprecated Polynomial.Splits.splits_of_dvd (since := "2025-11-25")]

theorem Polynomial.splits_of_splits_of_dvd {R : Type u_1} [CommRing R] {f g : Polynomial R} [IsDomain R] (hg : g.Splits) (hg₀ : g ≠ 0) (hfg : f ∣ g) : f.Splits

Alias of Polynomial.Splits.splits_of_dvd.

theorem Polynomial.splits_of_splits_gcd_left {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) [DecidableEq K] {f g : Polynomial K} (hf0 : f ≠ 0) (hf : (map i f).Splits) : (map i (EuclideanDomain.gcd f g)).Splits

theorem Polynomial.splits_of_splits_gcd_right {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) [DecidableEq K] {f g : Polynomial K} (hg0 : g ≠ 0) (hg : (map i g).Splits) : (map i (EuclideanDomain.gcd f g)).Splits

theorem Polynomial.splits_prod_iff {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) {ι : Type u} {s : ι → Polynomial K} {t : Finset ι} : (∀ j ∈ t, s j ≠ 0) → ((map i (∏ x ∈ t, s x)).Splits ↔ ∀ j ∈ t, (map i (s j)).Splits)

theorem Polynomial.degree_eq_one_of_irreducible_of_splits {K : Type v} [Field K] {p : Polynomial K} (hp : Irreducible p) (hp_splits : (map (RingHom.id K) p).Splits) : p.degree = 1

theorem Polynomial.exists_root_of_splits {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) {f : Polynomial K} (hs : (map i f).Splits) (hf0 : f.degree ≠ 0) : ∃ (x : L), eval₂ i x f = 0

theorem Polynomial.roots_ne_zero_of_splits {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) {f : Polynomial K} (hs : (map i f).Splits) (hf0 : f.natDegree ≠ 0) : (map i f).roots ≠ 0

def Polynomial.rootOfSplits {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) {f : Polynomial K} (hf : (map i f).Splits) (hfd : f.degree ≠ 0) : L

Pick a root of a polynomial that splits. This version is for polynomials over a field and has simpler assumptions.

Equations

• Polynomial.rootOfSplits i hf hfd = Polynomial.rootOfSplits' i hf ⋯

theorem Polynomial.rootOfSplits'_eq_rootOfSplits {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) {f : Polynomial K} (hf : (map i f).Splits) (hfd : (map i f).degree ≠ 0) : rootOfSplits' i hf hfd = rootOfSplits i hf ⋯

rootOfSplits' is definitionally equal to rootOfSplits.

theorem Polynomial.map_rootOfSplits {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) {f : Polynomial K} (hf : (map i f).Splits) (hfd : f.degree ≠ 0) : eval₂ i (rootOfSplits i hf hfd) f = 0

theorem Polynomial.natDegree_eq_card_roots {K : Type v} {L : Type w} [Field K] [Field L] {p : Polynomial K} {i : K →+* L} (hsplit : (map i p).Splits) : p.natDegree = (map i p).roots.card

theorem Polynomial.degree_eq_card_roots {K : Type v} {L : Type w} [Field K] [Field L] {p : Polynomial K} {i : K →+* L} (p_ne_zero : p ≠ 0) (hsplit : (map i p).Splits) : p.degree = ↑(map i p).roots.card

theorem Polynomial.roots_map {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) {f : Polynomial K} (hf : f.Splits) : (map i f).roots = Multiset.map (⇑i) f.roots

theorem Polynomial.Splits.mem_subfield_of_isRoot {K : Type v} [Field K] (F : Subfield K) {f : Polynomial ↥F} (hnz : f ≠ 0) (hf : f.Splits) {x : K} (hx : (map F.subtype f).IsRoot x) : x ∈ F

theorem Polynomial.image_rootSet {R : Type u_1} {K : Type v} {L : Type w} [CommRing R] [Field K] [Field L] [Algebra R K] [Algebra R L] {p : Polynomial R} (h : (map (algebraMap R K) p).Splits) (f : K →ₐ[R] L) : ⇑f '' p.rootSet K = p.rootSet L

theorem Polynomial.adjoin_rootSet_eq_range {R : Type u_1} {K : Type v} {L : Type w} [CommRing R] [Field K] [Field L] [Algebra R K] [Algebra R L] {p : Polynomial R} (h : (map (algebraMap R K) p).Splits) (f : K →ₐ[R] L) : Algebra.adjoin R (p.rootSet L) = f.range ↔ Algebra.adjoin R (p.rootSet K) = ⊤

@[deprecated Polynomial.Splits.eq_prod_roots (since := "2025-11-25")]

theorem Polynomial.eq_prod_roots_of_splits {R : Type u_1} [CommRing R] {f : Polynomial R} [IsDomain R] (hf : f.Splits) : f = C f.leadingCoeff * (Multiset.map (fun (x : R) => X - C x) f.roots).prod

Alias of Polynomial.Splits.eq_prod_roots.

@[deprecated Polynomial.Splits.eq_prod_roots (since := "2025-11-25")]

theorem Polynomial.eq_prod_roots_of_splits_id {R : Type u_1} [CommRing R] {f : Polynomial R} [IsDomain R] (hf : f.Splits) : f = C f.leadingCoeff * (Multiset.map (fun (x : R) => X - C x) f.roots).prod

Alias of Polynomial.Splits.eq_prod_roots.

theorem Polynomial.Splits.dvd_of_roots_le_roots {K : Type v} [Field K] {p q : Polynomial K} (hp : p.Splits) (hp0 : p ≠ 0) (hq : p.roots ≤ q.roots) : p ∣ q

theorem Polynomial.Splits.dvd_iff_roots_le_roots {K : Type v} [Field K] {p q : Polynomial K} (hp : p.Splits) (hp0 : p ≠ 0) (hq0 : q ≠ 0) : p ∣ q ↔ p.roots ≤ q.roots

theorem Polynomial.aeval_eq_prod_aroots_sub_of_splits {K : Type v} {L : Type w} [Field K] [Field L] [Algebra K L] {p : Polynomial K} (hsplit : (map (algebraMap K L) p).Splits) (v : L) : (aeval v) p = (algebraMap K L) p.leadingCoeff * (Multiset.map (fun (a : L) => v - a) (p.aroots L)).prod

theorem Polynomial.eval_eq_prod_roots_sub_of_splits_id {K : Type v} [Field K] {p : Polynomial K} (hsplit : p.Splits) (v : K) : eval v p = p.leadingCoeff * (Multiset.map (fun (a : K) => v - a) p.roots).prod

theorem Polynomial.eq_prod_roots_of_monic_of_splits_id {K : Type v} [Field K] {p : Polynomial K} (m : p.Monic) (hsplit : p.Splits) : p = (Multiset.map (fun (a : K) => X - C a) p.roots).prod

theorem Polynomial.aeval_eq_prod_aroots_sub_of_monic_of_splits {K : Type v} {L : Type w} [Field K] [Field L] [Algebra K L] {p : Polynomial K} (m : p.Monic) (hsplit : (map (algebraMap K L) p).Splits) (v : L) : (aeval v) p = (Multiset.map (fun (a : L) => v - a) (p.aroots L)).prod

theorem Polynomial.eval_eq_prod_roots_sub_of_monic_of_splits_id {K : Type v} [Field K] {p : Polynomial K} (m : p.Monic) (hsplit : p.Splits) (v : K) : eval v p = (Multiset.map (fun (a : K) => v - a) p.roots).prod

theorem Polynomial.eq_X_sub_C_of_splits_of_single_root {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) {x : K} {h : Polynomial K} (h_splits : (map i h).Splits) (h_roots : (map i h).roots = {i x}) : h = C h.leadingCoeff * (X - C x)

theorem Polynomial.mem_lift_of_splits_of_roots_mem_range (R : Type u_1) {K : Type v} [CommRing R] [Field K] [Algebra R K] {f : Polynomial K} (hs : f.Splits) (hm : f.Monic) (hr : ∀ a ∈ f.roots, a ∈ (algebraMap R K).range) : f ∈ lifts (algebraMap R K)

theorem Polynomial.splits_of_natDegree_eq_two {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) {f : Polynomial K} {x : L} (h₁ : f.natDegree = 2) (h₂ : eval₂ i x f = 0) : (map i f).Splits

A polynomial of degree 2 with a root splits.

theorem Polynomial.splits_of_degree_eq_two {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) {f : Polynomial K} {x : L} (h₁ : f.degree = 2) (h₂ : eval₂ i x f = 0) : (map i f).Splits

theorem Polynomial.splits_of_exists_multiset {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) {f : Polynomial K} {s : Multiset L} (hs : map i f = C (i f.leadingCoeff) * (Multiset.map (fun (a : L) => X - C a) s).prod) : (map i f).Splits

theorem Polynomial.splits_of_splits_id {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) {f : Polynomial K} (h : (map (RingHom.id K) f).Splits) : (map i f).Splits

theorem Polynomial.splits_of_comp {F : Type u} {K : Type v} {L : Type w} [Field K] [Field L] [Field F] (i : K →+* L) (j : L →+* F) {f : Polynomial K} (h : (map (j.comp i) f).Splits) (roots_mem_range : ∀ a ∈ (map (j.comp i) f).roots, a ∈ j.range) : (map i f).Splits

theorem Polynomial.splits_id_of_splits {K : Type v} {L : Type w} [Field K] [Field L] (i : K →+* L) {f : Polynomial K} (h : (map i f).Splits) (roots_mem_range : ∀ a ∈ (map i f).roots, a ∈ i.range) : (map (RingHom.id K) f).Splits

theorem Polynomial.splits_comp_of_splits {R : Type u_1} {K : Type v} {L : Type w} [CommRing R] [Field K] [Field L] (i : R →+* K) (j : K →+* L) {f : Polynomial R} (h : (map i f).Splits) : (map (j.comp i) f).Splits

theorem Polynomial.splits_of_algHom {R : Type u_1} {K : Type v} {L : Type w} [CommRing R] [Field K] [Field L] [Algebra R K] [Algebra R L] {f : Polynomial R} (h : (map (algebraMap R K) f).Splits) (e : K →ₐ[R] L) : (map (algebraMap R L) f).Splits

theorem Polynomial.splits_of_isScalarTower {R : Type u_1} {K : Type v} (L : Type w) [CommRing R] [Field K] [Field L] [Algebra R K] [Algebra R L] {f : Polynomial R} [Algebra K L] [IsScalarTower R K L] (h : (map (algebraMap R K) f).Splits) : (map (algebraMap R L) f).Splits

theorem Polynomial.splits_iff_card_roots {K : Type v} [Field K] {p : Polynomial K} : p.Splits ↔ p.roots.card = p.natDegree

A polynomial splits if and only if it has as many roots as its degree.

theorem Polynomial.eval₂_derivative_of_splits {K : Type v} {L : Type w} [Field K] [Field L] [DecidableEq L] {P : Polynomial K} {f : K →+* L} (hP : (map f P).Splits) (x : L) : eval₂ f x (derivative P) = f P.leadingCoeff * (Multiset.map (fun (a : L) => (Multiset.map (fun (x_1 : L) => x - x_1) ((map f P).roots.erase a)).prod) (map f P).roots).sum

theorem Polynomial.aeval_derivative_of_splits {K : Type v} {L : Type w} [Field K] [Field L] [Algebra K L] [DecidableEq L] {P : Polynomial K} (hP : (map (algebraMap K L) P).Splits) (r : L) : (aeval r) (derivative P) = (algebraMap K L) P.leadingCoeff * (Multiset.map (fun (a : L) => (Multiset.map (fun (x : L) => r - x) ((P.aroots L).erase a)).prod) (P.aroots L)).sum

theorem Polynomial.eval_derivative_of_splits {K : Type v} [Field K] [DecidableEq K] {P : Polynomial K} (hP : P.Splits) (r : K) : eval r (derivative P) = P.leadingCoeff * (Multiset.map (fun (a : K) => (Multiset.map (fun (x : K) => r - x) (P.roots.erase a)).prod) P.roots).sum

theorem Polynomial.aeval_root_derivative_of_splits {K : Type v} {L : Type w} [Field K] [Field L] [Algebra K L] [DecidableEq L] {P : Polynomial K} (hmo : P.Monic) (hP : (map (algebraMap K L) P).Splits) {r : L} (hr : r ∈ P.aroots L) : (aeval r) (derivative P) = (Multiset.map (fun (a : L) => r - a) ((P.aroots L).erase r)).prod

Let P be a monic polynomial over K that splits over L. Let r : L be a root of P. Then $P'(r) = \prod_{a}(r-a)$, where the product in the RHS is taken over all roots of P in L, with the multiplicity of r reduced by one.

theorem Polynomial.eval_derivative_eq_eval_mul_sum_of_splits {K : Type v} [Field K] {p : Polynomial K} {x : K} (h : p.Splits) (hx : eval x p ≠ 0) : eval x (derivative p) = eval x p * (Multiset.map (fun (z : K) => 1 / (x - z)) p.roots).sum

theorem Polynomial.eval_derivative_div_eval_of_ne_zero_of_splits {K : Type v} [Field K] {p : Polynomial K} {x : K} (h : p.Splits) (hx : eval x p ≠ 0) : eval x (derivative p) / eval x p = (Multiset.map (fun (z : K) => 1 / (x - z)) p.roots).sum

theorem Polynomial.coeff_zero_eq_leadingCoeff_mul_prod_roots_of_splits {K : Type v} [Field K] {P : Polynomial K} (hP : P.Splits) : P.coeff 0 = (-1) ^ P.natDegree * P.leadingCoeff * P.roots.prod

theorem Polynomial.coeff_zero_eq_prod_roots_of_monic_of_splits {K : Type v} [Field K] {P : Polynomial K} (hmo : P.Monic) (hP : P.Splits) : P.coeff 0 = (-1) ^ P.natDegree * P.roots.prod

If P is a monic polynomial that splits, then coeff P 0 equals the product of the roots.

theorem Polynomial.nextCoeff_eq_neg_sum_roots_mul_leadingCoeff_of_splits {K : Type v} [Field K] {P : Polynomial K} (hP : P.Splits) : P.nextCoeff = -P.leadingCoeff * P.roots.sum

theorem Polynomial.nextCoeff_eq_neg_sum_roots_of_monic_of_splits {K : Type v} [Field K] {P : Polynomial K} (hmo : P.Monic) (hP : P.Splits) : P.nextCoeff = -P.roots.sum

If P is a monic polynomial that splits, then P.nextCoeff equals the negative of the sum of the roots.

@[deprecated Polynomial.coeff_zero_eq_prod_roots_of_monic_of_splits (since := "2025-10-08")]

theorem Polynomial.prod_roots_eq_coeff_zero_of_monic_of_splits {K : Type v} [Field K] {P : Polynomial K} (hmo : P.Monic) (hP : P.Splits) : P.coeff 0 = (-1) ^ P.natDegree * P.roots.prod

Alias of Polynomial.coeff_zero_eq_prod_roots_of_monic_of_splits.

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If P is a monic polynomial that splits, then coeff P 0 equals the product of the roots.

@[deprecated Polynomial.nextCoeff_eq_neg_sum_roots_of_monic_of_splits (since := "2025-10-08")]

theorem Polynomial.sum_roots_eq_nextCoeff_of_monic_of_split {K : Type v} [Field K] {P : Polynomial K} (hmo : P.Monic) (hP : P.Splits) : P.nextCoeff = -P.roots.sum

Alias of Polynomial.nextCoeff_eq_neg_sum_roots_of_monic_of_splits.

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If P is a monic polynomial that splits, then P.nextCoeff equals the negative of the sum of the roots.