Results 1 to 8 of 8
Like Tree1Thanks
  • 1 Post By emakarov

Math Help - Sequences

  1. #1
    Junior Member
    Joined
    Feb 2013
    From
    Brampton
    Posts
    29

    Sequences

    1) Determine whether each recursive formula defines an arithmetic sequence,if it is arithmetic state the first five terms
    a) T^1=1, t^n =2t^n-1-n+2
    how do we know if its arithmetic ? Pleasehelp
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    Oct 2009
    Posts
    5,517
    Thanks
    771

    Re: Sequences

    Quote Originally Posted by darkangel06 View Post
    a) T^1=1, t^n =2t^n-1-n+2
    First, please explain how we are supposed to decide whether t^n-1-n+2 means tn-1-n+2, tn-1-n+2, tn-1-n+2 or tn-1-n+2. Second, you can calculate the first several terms of the sequence and make a hypothesis whether it is arithmetic. Then it can be proved.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Feb 2013
    From
    Brampton
    Posts
    29

    Re: Sequences

    I got that can you help me with this :
    The 5th term of a geometric sequence is 45 and the 8th term is 360 determine the 20th term
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,422
    Thanks
    1331

    Re: Sequences

    Quote Originally Posted by darkangel06 View Post
    I got that can you help me with this :
    The 5th term of a geometric sequence is 45 and the 8th term is 360 determine the 20th term
    The nth term, t_n, of a geometric sequence, with first term a and common multiple r, is t_n= ar^{n-1}. Surely you knew that?

    So the 5 term is ar^4= 45 and the 8th term is ar^7= 360. Use those to determine the values of a and r and the finnd a_{20}= ar^{19}.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member
    Joined
    Feb 2013
    From
    Brampton
    Posts
    29

    Re: Sequences

    Do i divide them ?
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    Joined
    Oct 2009
    Posts
    5,517
    Thanks
    771

    Re: Sequences

    Quote Originally Posted by darkangel06 View Post
    Do i divide them ?
    Don't worry: if you do, the paper won't burst into flames. In other words, why don't you try?
    Thanks from Shakarri
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Junior Member
    Joined
    Feb 2013
    From
    Brampton
    Posts
    29

    Re: Sequences

    I dont get how to find a and r
    Follow Math Help Forum on Facebook and Google+

  8. #8
    MHF Contributor
    Joined
    Oct 2009
    Posts
    5,517
    Thanks
    771

    Re: Sequences

    ar7 = 360 and ar4 = 45. Divide the first equation by the second one, i.e., divide the left-hand sides and then the right-hand sides and equate the results. Alternatively, express a from the second equation: a = 45 / r4 and substitute it into the first equation.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Convergence in sequences of sequences
    Posted in the Differential Geometry Forum
    Replies: 4
    Last Post: October 19th 2010, 07:28 AM
  2. Sequences and the sequences' arithmetics
    Posted in the Differential Geometry Forum
    Replies: 1
    Last Post: October 6th 2010, 09:31 PM
  3. Sequences
    Posted in the Differential Geometry Forum
    Replies: 1
    Last Post: October 4th 2009, 03:32 PM
  4. Monotone sequences and Cauchy sequences
    Posted in the Differential Geometry Forum
    Replies: 3
    Last Post: March 21st 2009, 08:59 PM
  5. Replies: 5
    Last Post: January 16th 2008, 04:51 PM

Search Tags


/mathhelpforum @mathhelpforum