proposition: Lemma BQprod_eq2r: z <> \0q -> x *q z = y *q z -> x = y.
proof: Proof. move => qgt0x h; rewrite - (BQdiv_prod zq xq qgt0x) - (BQdiv_prod zq yq qgt0x). by rewrite BQprodC h BQprodC. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)