Question

Using the graph below, what are the common ratio and the general term equation, an, of the geometric sequence?

Hint: an = a1(r)n − 1, where a1 is the first term and r is the common ratio.

OPTIONS:
r = 1/2, a sub n = -16 (1/2) to the power of n-1
r = −2, an = −16(−2)n − 1
r = 2, an = −16(2)n − 1
r = -1/2, a sub n = -16 (-1/2) to the power of n-1

Answer 1

r  = -8/-16  = -4/-8  = 1/2  and the first term is -16 (when n = 1)

so an  = -16 (1/2)^(n-1)

The first option.