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Homework Help: Group Theory

  1. Feb 25, 2009 #1
    If H is a subgroup of G then N(H) is defined as { x belonging to G | xHx^-1 = H }. If P is p-Sylow subgroup of G, then prove that N(N(P)) = N(P).
  2. jcsd
  3. Feb 25, 2009 #2
    Re: Gruop Theory

    You need to prove both directions.
    N(P) < N(N(P)) is obvious.

    To show N(N(P)) < N(P), you might need to use the fact that P is normal in N(P), which implies the only Sylow p-subgroup of N(P) is P itself.
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