Answer:
-20480
Explanation:
You want the 12th term of the geometric sequence 10, -20, 40, ....
N-th term
The n-th term of a geometric sequence is ...
an = a1(r^(n-1))
where a1 is the first term and r is the common ratio.
The given sequence has first term a1 = 10, and common ratio r = -20/10 = -2. So, the 12th term is ...
a12 = 10(-2)^(12 -1) = -20480
The 12th term of the sequence is -20480.
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