The formula which used to describe the sequence is f(x)=1.2(2.5)ˣ⁻¹.
The given sequence is 1.2,3,7.5,18.75.
In geometric series, the ratio of two consecutive terms remains the same and this ratio is known as common ratio. a₁ is the first term of a geometric sequence and r is the common ratio, then the general term of the geometric sequence is of the form:
f(x)=a₁⋅rˣ⁻¹.
In the given sequence, a₁=1.2, a₂=3, a₃=7.5 and a₄=18.75.
Find the common ratio by
r=(aₙ₊₁)÷aₙ
r=a₂÷a₁
r=3÷1.2
r=2.5
Substitute the values in the general formula of geometric sequence.
f(x)=(1.2)(2.5)ˣ⁻¹
Hence, the formula which used to describe the sequence 1.2,3,7.5,18.75 is f(x)=(1.2)(2.5)ˣ⁻¹.
Learn more about Geometric Sequence from here brainly.com/question/1509142
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