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

A

Explanation:

100% righttt

Answer 2

It's geometric sequence:

`a_1=1.2,\ a_2=3,\ a_3=7.5,\ a_4=18.75,\ ....`

Calculate the common ratio:

`r=(a_(n+1))/(a_n)\to r=(3)/(1.2)=2.5`

The explicit formula of geometric sequence:

`a_n=a_1r^(n-1)\to f(x)=a_1r^(x-1)`

Substitute:

`a_1=1.2,\ r=2.5\\\\f(x)=1.2\left(2.5)^(x-1)`

Answer: "f(x) = 1.2(2.5)x-1"