Question

Find an explicit rule for the nth term of a geometric sequence where the second and fifth terms are -6 and 162, respectively.

A; an = 2 • 3n - 1
B; an = 2 • (-3)n - 1
C; an = 2 • 3n
D; an = 2 • (-3)n + 1

Answer 1

The answer is B, I have just confirmed it.

Answer 2

5th term / 2nd term = r^4 / r = r^3

r^3 = 162/-6 = -27

so r = -3

a1 * r-3 = -6 so first term = 2

an = 2. (-3)^(n-1) Answer

Its B