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Homework Help: Arithmetic Sequence

  1. Nov 16, 2012 #1
    1. The problem statement, all variables and given/known data
    In an arithmetic sequence, the 11th term is 53 and the sum ofof the 5th and 7th terms is 56. Find the first 3 terms of the sequence.

    2. Relevant equations

    3. The attempt at a solution

    I'm trying to use the formula: tn= t1+(n-1)d but dont have right numbers. please show me step by step would be really helpful. Thanks
  2. jcsd
  3. Nov 16, 2012 #2


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    What is the 11th term of the sequence, in terms of t1 and d?
    What are the 5th and 7th terms?

  4. Nov 16, 2012 #3


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    Gold Member

    This problem description has two unknown values which need to be solved. You can find a system of equations using information about the 11th term and the relationship between the 5th and 7th terms. Your unknown numbers to solve for first are d and t1.

    The relevant equation for part 2 of the homework template is tn=t1+(n-1)d
  5. Nov 17, 2012 #4
    I'll give you an even bigger hint than Symbol and ehild gave:
    a(n) = a1 + (n-1)d
    substitute 11....
    53 = a1+10d
    you can do the rest ;)

    Thanks and good luck, Bonaparte
  6. Nov 17, 2012 #5


    Staff: Mentor

    From the PF rules:
    In other words, we don't provide step-by-step solutions. We'll help you with the work you do.
  7. Nov 17, 2012 #6
    okay thanks
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