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Math Help - recurrence formula

  1. #1
    CPR
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    recurrence formula

    Find the explicit formula for the recursive sequence using backtracking
    d1 = 3
    dn= -2dn-1

    Im thinking I will have (-6, 12, -24, 48,..)
    dn = -2dn-1
    = -2dn-1 + 1
    = -2 (-2dn-1 +1) +1


    but I do not know what else to do to end with a formula. Please show me what my formula will be

    * all the (n-1) should be subscripts, do know how to get it to subscript here in this window
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  2. #2
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    Hello, CPR!

    Find the explicit formula for the recursive sequence using backtracking:
    . . d_1 \:=\:3,\;\;\;d_n\:=\:\text{-}2\!\cdot\!d_{n-1}

    Im thinking I will have: . 3,\:\text{-}6,\:12,\:\text{-}24,\:48,\:\hdots\qquad{\color{blue}\text{Right!}}
    I'm not familiar with "backtracking".


    This is a geometric sequence with first term a= 3, common ratio r = \text{-}2

    The general term is: . d_n\;=\;3\cdot(\text{-}2)^{n-1}

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  3. #3
    CPR
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    Thanks.
    but explain to me why the subscript n-1 is now the superscript in the general term formula.
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