Question

WILL GIVE FAN AND MEDAL
Find an equation for the nth term of a geometric sequence where the second and fifth terms are -8 and 512, respectively.

Answer 1

@TrojanPoem Would you happen to know how to solve this?

Answer 2

x_{2} = -8
x_{5} = 512

ar^2-1 = -8

ar^5-1 = 512

ar = -8

ar^4 = 512

divide both eqn

r^3 = 64
r = 4

a = -2

eqn = -2 (4)^(n-1)

Answer 3

so 2(-4)^n-1 makes sense?