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Find the rule for this geometric sequence r=3 a3=-12

User JonoJames
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Answer:

-4 * 3^(n-1)

Explanation:

The rule for a geometric sequence is given by the formula an = a1 * r^(n-1), where a1 is the first term, r is the common ratio, and n is the term number. To find the common ratio, we can use the formula r = a2/a1 = a3/a2, since any two consecutive terms in a geometric sequence have the same ratio.

Given that a3 = -12 and r = 3, we can solve for a1 as follows:

a3 = a1 * r^(3-1)

-12 = a1 * 3^2

a1 = -4

Therefore, the rule for this geometric sequence is an = -4 * 3^(n-1).

User Rjohnston
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