proposition: Lemma mxcolB m (C_ C'_ : forall i, 'M[V]_(p_ i, m)) : \mxcol_i (C_ i - C'_ i) = \mxcol_i (C_ i) - \mxcol_i (C'_ i).
proof: Proof. by apply/matrixP=> i j; rewrite !mxE. 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)