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What is the recursive formula for this geometric sequence?

4, -12, 36, -108, ...
A) A: a_n = 4, Jan - 2n-1, -4
B) B: a_n = 18, 2n-1 • (-3)
C) C: a_n = 4, - 4, Tan - 8-1 • (-3)
D) D: a_n = 1, 2n-1 • (-3)

1 Answer

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Final answer:

The recursive formula for the sequence 4, -12, 36, -108, ... is given by a_n = a_(n-1) * (-3), with a_1 = 4, which most closely matches option C in the provided choices.

Step-by-step explanation:

The recursive formula for the given geometric sequence, which is 4, -12, 36, -108, ..., can be determined by recognizing the pattern that each term is multiplied by -3 to obtain the next term. The first term of the sequence is 4. To find the general recursive formula, we define it as a function of the previous term. So, the recursive formula would be an = -3 × an-1, with the first term given by a1 = 4. This is not explicitly stated in any of the options provided, but the correct structure can be observed in option C: an = an-1 × (-3), a1 = 4.

User Kaloyan Kosev
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