Arithmetic Sequence
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Arithmetic Sequence

Find the formula for the 11th term of the sequence in which a1 = 6 and the common ratio is -3.

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Arithmetic Sequence

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May 20, 2011
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Arithmetic Sequence
by: Staff


The question:

Find the formula for the 11th term of the sequence in which a1 = 6 and the common ratio is -3.


The answer:

The term “common ratio” is the term used with a geometric sequence.

An arithmetic sequence has the form:

a_n = a_1 + (n - 1) * (d)


a_n = a with a subscript of n (this is the nth term in the series)

a_1 = a with a subscript of 1 (this is the 1st term in the series)

n = number of terms

d = difference between consecutive terms


Applying the notation to your problem
Assuming you actually meant “difference between consecutive terms” rather than “common ratio”

a_1 = 6

d = difference between consecutive terms = -3


a_n = a_1 + (n - 1) * (d)

a_11 = 6 + (11 - 1) * (-3)

a_11 = 6 + (10) * (-3)

a_11 = 6 - 30

a_11 = -24



the final answer is: a_11 = -24





Thanks for writing.

Staff
www.solving-math-problems.com



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