proposition: Lemma mxblockB (B_ B'_ : forall i j, 'M[V]_(p_ i, q_ j)) : \mxblock_(i, j) (B_ i j - B'_ i j) = \mxblock_(i, j) (B_ i j) - \mxblock_(i, j) (B'_ i j).
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)