### Home > A2C > Chapter 12 > Lesson 12.4.1 > Problem12-165

12-165.
1. Evaluate these infinite geometric series if possible. If it is not possible, explain. Homework Help ✎

1. 8 + 4 + 2 + …

2. 3 + 9 + 27 + 81 + …

Find the common ratio.

$\frac{4}{8}=\frac{1}{2}$

$\frac{2}{4}=\frac{1}{2}$

Use the equation for an infinite geometric series:

$\sum_{n=1}^{\infty}ar^{n-1}=\frac{a}{1-r}$

16

See part (a).

Not possible. r > 1, and the terms keep increasing.