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If $|G|=p^{n}$

Then

Why is it that every subgroup of order $p^{n-1}$ is normal?

MrDi
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    Because it is a subgroup of index the smallest prime dividing the order of the group. Or because it cannot be self-normalizing since the group is nilpotent. – Tobias Kildetoft Apr 18 '16 at 07:32

1 Answers1

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A subgroup of index $p$ where $p$ is the smallest prime dividing the order of the group is a normal subgroup.

Upstart
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