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The sum of the 1st nine terms of an arithmetic series is 216. The 1st,3rd and the 7th terms of series form the 1st three terms of a geometric series. Find the 1st term and the constant difference of the arithmetic series ?

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  1. just write what they told you:

    9/2 (2a+8d) = 216
    (a+2d)/(a) = (a+6d)/(a+2d)

    Now solve for a and d.

    Now, just for precision, you mean arithmetic sequence. A series is the sequence of partial sums of a sequence. For example,

    sequence: 3,7,11,15,19,...
    series: 3,10,21,36,55,...

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  2. The third term of an arithmetic sequence is 14 and the ninth term is -1 find the first four term of the sequence

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