Definition Dmult :
  forall (a : Term A n) (nZa : ~ zeroP (A:=A) A0 eqA (n:=n) a),
  list (Term A n) -> list (Term A n) -> list (Term A n).

Theorem Rminus_is_mult : forall (r p q : list (Term A n)) (a : Term A n) (nZa : ~ zeroP (A:=A) A0 eqA (n:=n) a), canonical A0 eqA ltM p -> canonical A0 eqA ltM q -> canonical A0 eqA ltM r -> divPp a r -> eqP A eqA n (Rminus a nZa p q r) (minuspf A A0 A1 eqA invA minusA multA eqA_dec n ltM ltM_dec p (Dmult a nZa r q)).