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Help with series and sequences C1 AS Maths please? watch

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    A sequence of numbers a1, a2, a3… is defined by
    an+1 = 5an – 3, n>1
    given that a2 = 7
    find the value of a1

    The only thing I can think of is making n = 0
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    Substitute n = 1 into the sequence and see if you can form an equation. The n > 1 is confusing, though, since I am not sure how you could get an answer with anything other than n = 1...
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    (Original post by jessnoch)
    A sequence of numbers a1, a2, a3… is defined by
    an+1 = 5an – 3, n>1
    given that a2 = 7
    find the value of a1

    The only thing I can think of is making n = 0
    You know an+1; rearrange for an. (an will be a1 when an+1 is a2).

    I got a1 = 2. Let me know if you need any further help.
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    (Original post by jessnoch)
    A sequence of numbers a1, a2, a3… is defined by
    an+1 = 5an – 3, n>1
    given that a2 = 7
    find the value of a1

    The only thing I can think of is making n = 0
    I would do it this way by re-arranging for an:

    If an+1 = 5an - 3 and n>1

    Then -4an = -4

    so an = 1
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    (Original post by Gareth Owen)
    I would do it this way by re-arranging for an:

    If an+1 = 5an - 3 and n>1

    Then -4an = -4

    so an = 1
    I think you've misread the question. The equation given by the OP relates successive terms in the sequence, so it should say

    a_{n+1} = 5a_n - 3 for n > 1
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    (Original post by davros)
    I think you've misread the question. The equation given by the OP relates successive terms in the sequence, so it should say

    a_{n+1} = 5a_n - 3 for n > 1
    Yes you are right so A1 = 2 then. Agreed.
 
 
 
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