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How do you find the explicit formula for the arithmetic sequence, then find #a_14# given #a_1=9, d=-5#?

1 Answer

sankarankalyanam

Mar 17, 2018

#color(red)(a_14 = -56#

Explanation:

#a_1 = 9, d = -5#

#a_2 = a_1 + d = 9 - 5 = 4#

#a_3 = a_2 + d = a_1 + 2d = a_1 + (3-1) d = 4-5 = -1#

#:. a_n = a_1 + (n-1) * d# is the explicit formula.

#a_14 = a_1 + (14-1) * -5 = 9 - 65 = -56#

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