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Math Help - More Set Theory - HELP

  1. #1
    Junior Member
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    More Set Theory - HELP

    List the elements {a1, a2, a3, ...} where an is defined as a1 =1, an = na n-1, n E N, 1 < n < 7

    Out of 2 marks

    Need someone to check my answer please!

    Answer:

    When n=2, a3 = (2)a 2-1
    = (2) (1)
    = 2

    When n=3, a3 = (3)a 3-1
    = (3) (2)
    = 6

    When n=4, a4 = (4)a 4-1
    = (4) (6)
    = 24

    When n=5, a5 = (5)a 5-1
    = (5) (24)
    = 120

    When n=6, a6 = (6)a 6-1
    = (6) (120)
    = 720

    Therefore the solution set is {2,6,24,120,720} Is this correct?
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  2. #2
    Member Last_Singularity's Avatar
    Joined
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    Quote Originally Posted by cnmath16 View Post
    List the elements {a1, a2, a3, ...} where an is defined as a1 =1, an = na n-1, n E N, 1 < n < 7

    Out of 2 marks

    Need someone to check my answer please!

    Answer:

    When n=2, a3 = (2)a 2-1
    = (2) (1)
    = 2

    When n=3, a3 = (3)a 3-1
    = (3) (2)
    = 6

    When n=4, a4 = (4)a 4-1
    = (4) (6)
    = 24

    When n=5, a5 = (5)a 5-1
    = (5) (24)
    = 120

    When n=6, a6 = (6)a 6-1
    = (6) (120)
    = 720

    Therefore the solution set is {2,6,24,120,720} Is this correct?
    If I have read your notation correctly, is this what you mean?
    a_n = n a_{n-1} where a_1 = 1 and n \in N

    If so, your answer is correct. You are essentially calculating factorials of integers: each a_n = n! = n (n-1) ... (2) (1)
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