If Ā = ∩ F then show that A ⊆ Ā and Ā is the smallest closed set that contains A?

hi
my question is:
The closure of A is denoted by Ā. Ā = ∩ F, where the intersection is taken
over all the closed sets F that contain A.
show:
1- A ⊆ Ā
2- Ā is the smallest closed set that contains A
3 answers 3