Question

Find a12 for the geometric sequence -4, -2, -1, -1/2, ...

Answer 1

9514 1404 393

Answer:

-1/512

Explanation:

The first term is -4, and the common ratio is -2/-4 = 1/2. Then the n-th term is ...

an = -4·(1/2)^(n-1)

and the 12th term is ...

a12 = -4(1/2)^(12 -1) = -4/2048

a12 = -1/512