proposition: Lemma BQprod_eq2l: x <> \0q -> x *q y = x *q z -> y = z.
proof: Proof. move => qgt0x h; rewrite - (BQdiv_prod xq yq qgt0x). by rewrite - (BQdiv_prod xq zq qgt0x) h. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)