proposition: Lemma mxrank_opp m n (A : 'M_(m, n)) : \rank (- A) = \rank A.
proof: Proof. by rewrite -scaleN1r mxrank_scale_nz // 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)