Answer:

a9 = 32

Step-by-step explanation:

an = a1r^n-1

1 = 1/8r^4-1

1 = 1/8r^3

8(1) = (1/8r^3)(8)

8 = r³

___ ____

3 / 3 /

\/ 8 = \/ r³

2 = r

OR

r = 2

To find a9

an = a1r^n-1

a9 = 1/8 r^9-1

a9 = 1/8 (2)^8

a9 = 1/8 (256)

a9 = 32