Let (sn) be a sequence that converges.
(a) Show that if sn ≥ a for all but finitely many n,
then lim sn ≥ a.
(b) Show that if sn ≤ b for all but finitely many n,
then lim sn ≤ b.
(c) Conclude that if all but finitely many sn belong to [a,b],
then lim sn belongs to [a, b].