Question

Which of the following is the explicit formula for the geometric sequence 320, 80, 20, 5, ...?

G(n) = 320(¼)n-1
G(n) = 320(4)n-1
G(n) = 320(¼)n
G(n) = ¼(320)n-1

Answer 1

The first one hopefully :)

Explanation:

Answer 2

common ratio can be found by dividing the second term by the first term
80/320 = 0.25 (which is 1/4)

G(n) = a1 * r^(n-1)
a1 = first term = 320
r = common ratio = 1/4

so ur formula is : G(n) = 320(1/4)^n-1