Results 1 to 3 of 3

Math Help - Pre-calc-arithmetic sequence

  1. #1
    Junior Member
    Joined
    Jul 2008
    Posts
    38

    Pre-calc-arithmetic sequence

    in an arithmetic sequence t sub 2=6 , t sub 6=16 find t sub 12

    sorry i dont know how to do the sub thing.hopefully it makes sense.Thank you!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    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 ep78 View Post
    in an arithmetic sequence t sub 2=6 , t sub 6=16 find t sub 12

    sorry i dont know how to do the sub thing.hopefully it makes sense.Thank you!
    see here to see what the variables mean.

    since the general term is given by t_n = t_1 + (n - 1)d, you have

    t_2 = 6 = t_1 + d

    and

    t_6 = 16 = t_1 + 5d

    you can solve this system for t_1 and d and hence find t_{12} = t_1 + 11d
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor
    Prove It's Avatar
    Joined
    Aug 2008
    Posts
    11,570
    Thanks
    1428
    Quote Originally Posted by ep78 View Post
    in an arithmetic sequence t sub 2=6 , t sub 6=16 find t sub 12

    sorry i dont know how to do the sub thing.hopefully it makes sense.Thank you!
    For an arithmetic sequence...

    t_n = t_1 + (n - 1)d.

    You're told that t_2 = 6, so

    t_2 = t_1 + (2 - 1)d

    6 = t_1 + d

    and you're also told that t_6 = 16, so

    t_6 = t_1 + (6 - 1)d

    16 = t_1 + 5d.


    You now have 2 equations in 2 unknowns that you can solve simultaneously. Subtract equation 1 from equation 2 and you should find

    10 = 4d

    d = \frac{5}{2}.


    Substitute back into equation 1 to get

    6 = t_1 + \frac{5}{2}

    t_1 = \frac{7}{2}.


    Therefore t_n = \frac{7}{2} + (n - 1)\frac{5}{2}.


    What is t_{12}?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 2
    Last Post: August 24th 2010, 02:10 AM
  2. Arithmetic Sequence
    Posted in the Algebra Forum
    Replies: 4
    Last Post: February 4th 2010, 11:08 PM
  3. Arithmetic Sequence
    Posted in the Algebra Forum
    Replies: 3
    Last Post: February 2nd 2010, 07:14 PM
  4. Arithmetic sequence
    Posted in the Algebra Forum
    Replies: 2
    Last Post: February 10th 2007, 03:52 AM
  5. Replies: 12
    Last Post: November 15th 2006, 12:51 PM

Search Tags


/mathhelpforum @mathhelpforum