Theory of univariate polynomials

The main def is Polynomial.binomExpansion.

def Polynomial.powAddExpansion {R : Type u_1} [CommSemiring R] (x y : R) (n : ℕ) : { k : R // (x + y) ^ n = x ^ n + ↑n * x ^ (n - 1) * y + k * y ^ 2 }

(x + y)^n can be expressed as x^n + n*x^(n-1)*y + k * y^2 for some k in the ring.

def Polynomial.binomExpansion {R : Type u} [CommRing R] (f : Polynomial R) (x y : R) : { k : R // eval (x + y) f = eval x f + eval x (derivative f) * y + k * y ^ 2 }

A polynomial f evaluated at x + y can be expressed as the evaluation of f at x, plus y times the (polynomial) derivative of f at x, plus some element k : R times y^2.

def Polynomial.powSubPowFactor {R : Type u} [CommRing R] (x y : R) (i : ℕ) : { z : R // x ^ i - y ^ i = z * (x - y) }

x^n - y^n can be expressed as z * (x - y) for some z in the ring.

def Polynomial.evalSubFactor {R : Type u} [CommRing R] (f : Polynomial R) (x y : R) : { z : R // eval x f - eval y f = z * (x - y) }

For any polynomial f, f.eval x - f.eval y can be expressed as z * (x - y) for some z in the ring.