intros a b Q H'; inversion H'; auto.
apply reduceplus_cb1; auto.
Qed.

Theorem reduce_cb2 :
forall (a b : poly A0 eqA ltM) (Q : list (poly A0 eqA ltM)),
reduce A A0 A1 eqA invA minusA multA divA eqA_dec n ltM ltM_dec Q
(s2p A A0 eqA n ltM a) (s2p A A0 eqA n ltM b) ->
CombLinear (b :: Q) (s2p A A0 eqA n ltM a).