intros a b Q H' H'0 H'1.
cut (canonical A0 eqA ltM b);
[ intros Op1 | apply canonical_reduce with (1 := cs) (3 := H'); auto ].
case reduce_inv2 with (1 := cs) (3 := H'); auto;
(intros c E; elim E; intros d E0; elim E0; intros H'7 H'8; elim H'8;
intros H'9 H'10; elim H'10; intros H'11 H'12; clear H'10 H'8 E0 E);
auto.
apply
CombLinear_comp
with
(p := minuspf A A0 A1 eqA invA minusA multA eqA_dec n ltM ltM_dec a
(mults (A:=A) multA (n:=n) d c)); auto.
apply (eqp_sym _ _ _ _ _ _ _ _ _ cs n); auto.
Qed.

Theorem reduceplus_cb :
forall (a b : list (Term A n)) (Q : list (poly A0 eqA ltM)),
reduceplus A A0 A1 eqA invA minusA multA divA eqA_dec n ltM ltM_dec Q a b ->
canonical A0 eqA ltM a -> CombLinear Q a -> CombLinear Q b.