Results 1 to 3 of 3

Math Help - geometric sequences

  1. #1
    Newbie
    Joined
    Nov 2007
    Posts
    4

    Question geometric sequences

    hi all,


    Please help me .. I will have a test soon but I still don't know how to use geometric sequences to solve a repeated number. I've posted my question in several forums hoping someone would hlep me .. but .. no .. Thank you so much for helping me!


    1. Use the concepts of geometric sequences to write 1.264545454545..... as a rational number in the form a/b where a and b are integers.
    How would you solve this using geometric sequence?


    2. Write an expression for the apparent nth term of the sequence as a function of n: -2, 1, 6, 13, 22

    I noticed that these numbers are increment of 3, but I don't know how I should go about to have the first term as -2 and the rest as positive number
    Last edited by fallingsky26; November 5th 2007 at 12:31 PM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,712
    Thanks
    1642
    Awards
    1
    \begin{array}{l}<br />
 1.264545 \cdots  \\ <br />
 1 + \frac{{26}}{{100}} + \frac{{45}}{{10000}} + \frac{{45}}{{1000000}} +  \cdots  \\ <br />
 1 + \frac{{26}}{{100}} + \sum\limits_{k = 1}^\infty  {\frac{{45}}{{10^{2k + 2} }}}  \\ <br />
 \end{array}<br />
    Follow Math Help Forum on Facebook and Google+

  3. #3
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by fallingsky26 View Post
    hi all,


    Please help me .. I will have a test soon but I still don't know how to use geometric sequences to solve a repeated number. I've posted my question in several forums hoping someone would hlep me .. but .. no .. Thank you so much for helping me!


    1. Use the concepts of geometric sequences to write 1.264545454545..... as a rational number in the form a/b where a and b are integers.
    How would you solve this using geometric sequence?
    I will start you off.

    1.26 \overline{45} = 1 + 0.26 \overline{45}

    = 1 + 0.26 + 0.00 \overline{45}

    = 1 + \frac {26}{100} + \frac {45}{10^4} + \frac {45}{10^6} + \frac {45}{10^8} + \cdots

    = 1 + \frac {26}{100} + \frac {45}{10^4} \left( 1 + \frac 1{10^2} + \frac 1{10^4} + \frac 1{10^6} + \cdots \right)

    can you take it from here?

    1. Write an expression for the apparent nth term of the sequence as a function of n: -2, 1, 6, 13, 22

    I noticed that these numbers are increment of 3, but I don't know how I should go about to have the first term as -2 and the rest as positive number
    try to figure out a pattern (they are not all increments of 3)

    we start with -2, now note:

    1 = -2 + 3

    6 = 1 + 5

    13 = 6 + 7

    22 = 13 + 9

    notice anything?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Geometric sequences
    Posted in the Algebra Forum
    Replies: 1
    Last Post: April 28th 2009, 02:51 AM
  2. Geometric Sequences please help
    Posted in the Algebra Forum
    Replies: 2
    Last Post: November 8th 2008, 03:42 AM
  3. geometric sequences (please help)
    Posted in the Algebra Forum
    Replies: 4
    Last Post: November 6th 2008, 11:32 AM
  4. geometric sequences
    Posted in the Algebra Forum
    Replies: 2
    Last Post: November 4th 2008, 08:43 AM
  5. Replies: 5
    Last Post: January 16th 2008, 04:51 PM

Search Tags


/mathhelpforum @mathhelpforum