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 in_minuspf_spoly_in : forall a b : Term A n, eqT (ppc (A:=A) A1 (n:=n) a b) (multTerm (A:=A) multA (n:=n) a b) -> forall p q : list (Term A n), canonical A0 eqA ltM (pX a p) -> canonical A0 eqA ltM (pX b q) -> forall c : Term A n, In c (mults (A:=A) multA (n:=n) b p) -> In c (minuspf A A0 A1 eqA invA minusA multA eqA_dec n ltM ltM_dec (mults (A:=A) multA (n:=n) b p) (mults (A:=A) multA (n:=n) a q)).