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Lv 6
? asked in Science & MathematicsMathematics · 8 years ago

Can someone solve this word problem?

9th term is 11; 18th term is 29

Find the first term

find the common difference of the arithmetic sequence described.

Give a recursive formula for the sequence.

Find a formula for the nth term.

1 Answer

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  • ignoramus
    Lv 7
    8 years ago
    Favorite Answer

    So 9 terms (9 to 18) give a total difference of 18, hence the common difference = 18/9 = 2.

    Hence

    u(n + 1) = u(n) + 2

    Working backwards, the 9th term includes 8 of the common differences = 8 x 2 = 16.

    Hence term number 1 = 11 - 16 = -5

    so the nth term = -5 + 2n

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