Section PS_opp.
Context {K : AbsRing} {V : NormedModule K}.
Definition PS_opp (a : nat -> V) (n : nat) : V := opp (a n).

Lemma is_pseries_opp (a : nat -> V) (x :K) (l : V) :
is_pseries a x l -> is_pseries (PS_opp a) x (opp l).