proposition: Fact mulrzAC m n x : (x *~ n) *~ m = (x *~ m) *~ n.
proof: Proof. by rewrite !mulrzA_C mulrC. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat choice seq) mathcomp(fintype finfun bigop order ssralg countalg ssrnum) mathcomp(poly)