proposition: Lemma mul2I: injective (fun z : L => z *+ 2).
proof: Proof. have nz2 := nz2. by move=> x y; rewrite /= -mulr_natl -(mulr_natl y) => /mulfI->. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun ssrnat eqtype seq choice) mathcomp(div fintype path bigop finset prime order ssralg) mathcomp(poly polydiv mxpoly generic_quotient countalg) mathcomp(ssrnum closed_field ssrint archimedean rat intdiv) mathcomp(algebraics_fundamentals)