proposition: Lemma eqmx_opp m n (A : 'M_(m, n)) : (- A :=: A)%MS.
proof: Proof. by rewrite -scaleN1r; apply: eqmx_scale => //; rewrite oppr_eq0 oner_eq0. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrfun eqtype ssrnat seq choice) mathcomp(fintype finfun bigop finset fingroup perm order) mathcomp(div prime binomial ssralg finalg zmodp matrix)