proposition: Lemma deg2_poly_root1 : root p r1.
proof: Proof. apply/factor_theorem. by exists (a *: ('X - r2%:P)); rewrite deg2_poly_factor -!scalerAl mulrC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype bigop finset tuple) mathcomp(div ssralg countalg binomial)