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the 10th term of an arithmetic series is 34, and the sum of the first 20 terms is 710, determine the 25th term.

  • math -

    I will assume that you know the formulas for term(n) and sum(n) of an AS
    10 term is 34 ---> a+9d = 34
    sum of 20 terms is 710 ---> (20/2)[2a + 19d] = 710
    2a + 19d = 71
    double the first equation, then subract
    2a + 18d = 68
    d = 3
    back into 1st ---> a + 27 = 34
    a = 7

    term(25) = a+24d = 7 + 72 = 79

  • math -

    Thanks :) so much

  • math -

    uidont

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