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Anonymous
Anonymous asked in Science & MathematicsMathematics · 8 years ago

In terms of n, find the sum of the first n terms of the arithmetic sequence: -4, 5, 14, 23, 32, .....?

In terms of n, find the sum of the first n terms of the arithmetic sequence: -4, 5, 14, 23, 32, .....

Thanks!

4 Answers

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  • ?
    Lv 5
    8 years ago

    An=9(n-1)-4

    sum=9n(n+1)/2-13n

  • Vince 505
    Lv 6
    8 years ago

    This is an arithmetic series, in which there is a common difference (d) between one term and the next.

    In this case, d = 9

    Sum = n[a + d/2(n-1)]

    =n[ - 4 + 4.5 (n-1)]

    = 4.5n^2 - 8.5n

    = n (4.5n - 8.5)

    =½ n (9n -17)

  • Anonymous
    8 years ago

    -4+9n

  • Brigardo
    8 years ago

    9n -4

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