proposition: Lemma memv_add u v U V : u \in U -> v \in V -> u + v \in (U + V)%VS.
proof: Proof. by rewrite !memvK genmxE linearD; apply: addmx_sub_adds. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype bigop finfun tuple) mathcomp(ssralg matrix mxalgebra zmodp)