x * y.
Proof. by rewrite mulrN mulNr opprK. Qed.
Lemma mulN1r x : -1 * x = - x.Proof. by rewrite mulNr mul1r. Qed.Lemma mulrN1 x : x * -1 = - x.

(* Specifications: *)
Proof. exact: big_distrr. Qed.
Proof. by rewrite mulrnAl mul1r. Qed.
Proof. by rewrite mulrnAr mulr1. Qed.