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Math Help - geometric sequence help

  1. #1
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    geometric sequence help

    List the first four terms of a geometric sequence with t1 = 4 and tn = -3tn-1.
    How do I find r???
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  2. #2
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    Re: geometric sequence help

    Quote Originally Posted by dzomberg View Post
    List the first four terms of a geometric sequence with t_1 = 4 and t_n = -3t_{n-1}.
    How do I find r???
    Well t_2=-3(t_1). Now you post what you get!
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  3. #3
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    Re: geometric sequence help

    Hello, dzomberg!

    List the first four terms of a geometric sequence with:- t_1 = 4\,\text{ and }t_n = \text{-}3\!\cdot\!t_{n-1}

    How do I find r?

    Just read what you are given . . . and crank out the list.


    t_1 = 4 . . . The first term is 4.

    t_n = \text{-}3\!\cdot\!t_{n-1} . . . Each term is -3 times the preceding term.


    Therefore:

    . . \begin{array}{cccccc}t_1 &=& 4 &=& \;4\\ t_2 &=& \text{-}3(4) &=& \text{-}12 \\ t_3 &=& \text{-}3(\text{-}12) &=& \;36 \\ t_4 &=& \text{-}3(36) &=& \text{-}108 \end{array}
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    Re: geometric sequence help

    Quote Originally Posted by dzomberg View Post
    List the first four terms of a geometric sequence with t1 = 4 and tn = -3tn-1.
    How do I find r???
    ....And please learn to use LaTeX (as in our LaTeX help forum) or learn how to use parenthesis. tn = -3t(n-1) is a bit better anyway. t_n = -3t_(n - 1) would be best.

    -Dan
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