proposition: Lemma stableCmx (m n : nat) x (f : 'M[F]_(m, n)) : stablemx x%:M f.
proof: Proof. have [->|x_neq0] := eqVneq x 0; first by rewrite mul_scalar_mx scale0r sub0mx. by rewrite -![x%:M]scalemx1 eqmx_scale// submx_full// -sub1mx. 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)