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What is the 9th term of a geometric

sequence with a first term of 12 and a
common ratio of -3?

User Acromm
by
7.1k points

1 Answer

1 vote

Answer:

Explanation:

The formula for an explicit geometric sequence is


a_n=a_1*r^{n-1 where n is the position of the number in the sequence (ours will be 9 since we are looking for the 9th term), a1 is the first term in the sequence (ours is given as 12), and r is the common ratio (ours is given as -3). Filling all of that in to get the explicit formula we need:


a_n=12*(-3)^{n-1 and solving for the 9th term:


a_9=12*(-3)^8 which gives us, simplified a bit:


a_9=12(6561) so

a9 = 78,732

User Syed Ahsan Jaffri
by
8.3k points

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