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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

Respuesta :

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

The answer is B, I have just confirmed it.

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