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3 November, 03:49

The first term of an arithmetic sequence is - 12. The common difference of the sequence is 7. What is the sum of the first 30 terms of the sequence? Enter your answer in the box.

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  1. 3 November, 05:42
    0
    2685

    Step-by-step explanation:

    The nth term of an arithmetic sequence is:

    aₙ = a₁ + d (n - 1)

    where a₁ is the first term and d is the common difference.

    Here, a₁ = - 12 and d = 7:

    aₙ = - 12 + 7 (n - 1)

    aₙ = - 12 + 7n - 7

    aₙ = - 19 + 7n

    The sum of the first n terms of an arithmetic sequence is:

    S = (n/2) (a₁ + aₙ)

    First, we find the 30th term:

    a₃₀ = - 19 + 7 (30)

    a₃₀ = 191

    Now we find the sum:

    S = (30/2) (-12 + 191)

    S = 2685
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