Question 46999
<pre>4, -12, 36, -108


The common formula for a geometric sequence is {{{a*(r^(n-1))}}}

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*(r^(n-1))}}}

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

Let's substitute these values into our formula

{{{4*(r^(2-1))=-12}}} {{{4*(r))=-12}}}

4r = -12

r= -3

Hence, our common ratio is -3.


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