1.2, 3, 7.5, 18.75,
which formula can be used to describe the sequence?
a. f(x) = 1.2(2.5)^x – 1
b. f(x) = 2.5(1.2)^x – 1
c. f(x) = 1.2(2.5)^x
d. f(x) = 2.5(1.2)^x

Step-by-step explanation:

So looking at the choices, the problem is suggest it is geometric which means it has a common ratio.

The common ratio can be found by doing term divided by previous term. So let me pick a term and divide by it's previous term.  How about 3; so it's previous term is 1.2.  So 3 divded by 1.2 is 2.5 .

2.5 is the common ratio.  It will be the one that is the repeated factor, the one that contains the variable exponent.

The first term is 1.2.

The following is the formula for generating the terms in a geometric sequence:

A is the first term

r is the common ratio

So now we just plug in: