What is the closed form definition for 4, -12, 36, -108?

Hagen asked Jul 11, 2023

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23 votes

Hagen asked Jul 11, 2023

by Hagen

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25 votes

we see that

$\begin{gathered} (-12)/(4)=-3 \\ (36)/(-12)=-3 \\ (-108)/(36)=-3 \end{gathered}$

Then, we have a geometric sequence, and each time we need to muliply by -3 starting from 4, so the closed-form is

so, the answer is the second one.

Maduranga E answered Jul 15, 2023

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