intros a b c; case a; case b; case c; simpl in |- *; auto.
intuition.
Qed.

(* Specifications: *)
Theorem plusTerm_comp_r :
forall a b c : Term,
eqT c a -> eqT c b -> eqTerm a b -> eqTerm (plusTerm c a) (plusTerm c b).
Theorem plusTerm_com :
forall x y : Term, eqT x y -> eqTerm (plusTerm x y) (plusTerm y x).