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Homework Help: I want check my answers

  1. Jan 31, 2010 #1
    I want check my answer

    Q 1 : If the second term = 6 and fifteenth = 25 of sequence find the first term ?

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  2. jcsd
  3. Jan 31, 2010 #2


    Staff: Mentor

    Please type your work into the text entry box. Having to open an attachment is a pain in the butt, since I have to read your work on one window and post comments in another. It's much better if everything is in one place.

    You have
    Tn = a + (n - 1)d

    In the next line you have T25 = a + (15 - 1)d
    Why do you have 15 on the right side?

    In the 3rd line you have
    25 = a + 14d

    Where did the 25 come from?

    If you want help, please post the complete problem statement, using the standard template, together with your work.
  4. Jan 31, 2010 #3


    Staff: Mentor

    GRRR! Now I understand a little better what you're doing. You have part of the information in your first post and part in the attachment. If you had put all the information and your work in your post it would have been harder to miss.

    The problem statement, as I see it is this:
    Tn = a + (n - 1)d. The second term in this sequence is 6, and the 15th term is 25. What is the first term in this sequence?

    From the given information,
    T(2) = a + (2 - 1)d = 6, and
    T(15) = a + (15 - 1) d = 25

    So the problem boils down to finding the solution of
    a + d = 6
    a + 14d = 25

    The solution you have for d is incorrect.
  5. Jan 31, 2010 #4
    thanks D.Mark , I am sorry for annoying you
  6. Jan 31, 2010 #5


    Staff: Mentor

    I don't mind helping, but try not to make it hard for me and anyone else to give help.

    Have you figured out the solution to this system yet?
    a + d = 6
    a + 14d = 25
  7. Feb 1, 2010 #6
    a+14d = 25
    a+d = 6

    I Subtract the second equation from the first and solve for d.

    thanks D.Mark for helping me
  8. Feb 1, 2010 #7


    Staff: Mentor

    So what do you get? The value you got for d before (19/14) was incorrect.
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