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For the following geometric sequence, find the explicit formula.

{1, -3, 9, ...}

an = (-3) n - 1
an = -3 · an - 1 where a1 = 1
an = -1 · (-3) n - 1
an = -3 · an - 1 where a1 = -1

User Chad Befus
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1 Answer

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Answer:
a_n=(-3)^(n-1)

Explanation:

The common ratio is
r=-3.


a_n=a_1 \cdot r^(n-1)=1 \cdot (-3)^(n-1)=(-3)^(n-1)

User Msmafra
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