proposition: Lemma freegUN k x : - << k *g x >> = << -k *g x >>.
proof: Proof. by apply/eqP/freeg_eqP=> z; rewrite coeffN !coeffU mulNr. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop order generic_quotient) mathcomp(ssralg ssrnum ssrint)