college algebra word problem

Question

Write a recursive formula for the geometric sequence.

a_n = {−32, −16, −8, −4,   }

Answer 1

factor out -4 to get

(8,4,2,1,...)

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

-32 when n= 1, -4(2^3) = -4(8)

-16 when n=2, -4(2^2) = -4(4)

-8 when n=3 -4(2^1) = -4(2)

--4 when n=4 -4(2^0) = -4(1)

the nth term, a_n = -4(2^4-n)