The fifth term of an arithmetic sequence is 23 and the 12th term is 72? Determine the first three terms of the sequence and the nth term​

Question

The fifth term of an arithmetic sequence is 23 and the 12th term is 72? Determine the first three terms of the sequence and the nth term​

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Thiên Di 6 months 2021-07-24T19:04:37+00:00 1 Answers 7 views 0

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    2021-07-24T19:06:06+00:00

    Answer:

    the first term is a1

    the distance between the numbers is d

    we have:

    a5 = a1 + 4d = 23

    a12 = a1 + 11d = 72

    so we have the equation:

    a1 + 4d = 23

    a1 + 11d = 72

    => a1 = -5

    d = 7

    => an = -5 + 7(n – 1) = 7n – 12

    with an = 7n – 12

    => a2 = 2

    a3 = 9

    so the first three terms is -5; 2; 9

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Giải phương trình 1 ẩn: x + 2 - 2(x + 1) = -x . Hỏi x = ? ( )