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    Posted this earlier but no response? Any ideas on how to do these questions?


    3) a) Prove that if f : G → H is a group isomorphism, then for any element x ∈ G onehaso(x) = o(f(x)),
    where o(a) denotes the order of the element a.

    b) Based on the previous fact, prove that the groups C4 ad C2 × C2 are not isomorphic.
    HereCn = {1, t, · · · , t^(n−1) |tn = 1}is the cyclic group of order n.

    c) Prove that any group of order 4 is isomorphic either to the group C4 or C2 × C2.
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    gregorious

    poorform


    any ideas guys?
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    (Original post by maths10101)
    Posted this earlier but no response? Any ideas on how to do these questions?


    3) a) Prove that if f : G → H is a group isomorphism, then for any element x ∈ G onehaso(x) = o(f(x)),
    where o(a) denotes the order of the element a.
    Before the proper people get here, let |g| = n and |f(g)| = m, then:

    (f(g))^n = f(g^n) = f(e_G) = e_H so m | n.

    Then f(g^m) = (f(g))^m = e_H = f(e_G)

    use the fact that f is injective to finish off and conclude.
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    @Zacken ahh thanks mate! Helps a lot..any ideas on parts b and c?


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    @zacken
    Never mind, I got it in the end! Thanks 🤐


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    (Original post by maths10101)
    @zacken
    Never mind, I got it in the end! Thanks 🤐


    Posted from TSR Mobile
    Your tags aren't working, you need to type: @Zacken and then select my name from the drop down list by manually clicking on it, otherwise it I don't get a notification.
 
 
 
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