End Properties2.

(* Specifications: *)
Lemma Series_plus (a b : nat -> R) :
ex_series a -> ex_series b
-> Series (fun n => a n + b n) = Series a + Series b.
Lemma Series_minus (a b : nat -> R) :
ex_series a -> ex_series b
-> Series (fun n => a n - b n) = Series a - Series b.