SOLUTION: What is the common ration in the geometric sequence 4, -12, 36, -108, . . .?

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Question 46999This question is from textbook COLLEGE ALGEBRA
: What is the common ration in the geometric sequence 4, -12, 36, -108, . . .? This question is from textbook COLLEGE ALGEBRA

Answer by atif.muhammad(135) About Me  (Show Source):
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4, -12, 36, -108


The common formula for a geometric sequence is a%2A%28r%5E%28n-1%29%29

where a is the first term, r is the common ratio

In our case, a=4 -- 4 is the first term

So our formula now is: 4%2A%28r%5E%28n-1%29%29

We know that when n=2, our sequence number is -12.

Let's substitute these values into our formula

4%2A%28r%5E%282-1%29%29=-12 4%2A%28r%29%29=-12

4r = -12

r= -3

Hence, our common ratio is -3.