intros p; elim p; auto.
simpl in |- *; auto.
intros a l H a0 H0;
change
(eqP A eqA n (pX (multTerm (A:=A) multA (n:=n) a0 a) (mults a0 l))
(pX a l)) in |- *; auto.
apply (eqpP1 A eqA n); auto.
apply (eqTerm_sym _ _ _ _ _ _ _ _ _ cs n); apply T1_multTerm_l with (1 := cs);
auto.
Qed.

Theorem mults_invTerm :
forall (p : list (Term A n)) (a : Term A n),
eqTerm (A:=A) eqA (n:=n) a (T1 A1 n) ->
eqP A eqA n
(pluspf (A:=A) A0 (eqA:=eqA) plusA eqA_dec (n:=n) (ltM:=ltM) ltM_dec p
(mults (invTerm (A:=A) invA (n:=n) a) p)) (pO A n).