TITLE: Question about proving something about subgroup
QUESTION [0 upvotes]: $G$ is a group, and $\left\{H_i|i\in I\right\}$ is family os subgroups of $G$ (I is not a matrix or something similar...)
I need to prove that $$\bigcap_{i\in I}H_i$$ is a subgroup of $G$.
Any ides?
Thank you!

REPLY [4 votes]: This is a very standard problem.
http://groupprops.subwiki.org/wiki/Intersection_of_subgroups_is_subgroup
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