proposition: Lemma mul_mxcol_mxrow m (C_ : forall i, 'M[R]_(p_ i, m)) (R_ : forall j, 'M[R]_(m, q_ j)) : \mxcol_i C_ i*m \mxrow_j R_ j = \mxblock_(i, j) (C_ i *m R_ j).
proof: Proof. apply/mxblockP => i j; rewrite mxblockK. by rewrite submxblockEh -mul_submxrow -submxcol_mul mxcolK mxrowK. 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 countalg finalg zmodp)