Question

1.2, 3, 7.5, 18.75, ...

Which formula can be used to describe the sequence?

f(x) = 1.2(2.5)x – 1
f(x) = 2.5(1.2)x – 1
f(x) = 1.2(2.5)x
f(x) = 2.5(1.2)x

Answer 1

The sequence is geometric with first term 1.2 and common ratio 2.5, so
f(x) = 1.2·(2.5)^(x−1).

(That is the first choice.)