Which of the following is not a geometric sequence?

1,-3,9,-27,81

-7,-5.8,-4.6,-3.4,-2.2

-100 - 20 - 4, 4/5, 4/25

2.8,6.72,16.128,38.7072

-7,-5.8,-4.6,-3.4,-2.2

Step-by-step explanation:

A geometric sequence must have a common ratio.

-3 / 1 = - 3

9 / - 3 = - 3

-27 / 9 = - 3

81 / - 27 = - 3

The first sequence is a geometric sequence.

-5.8 / - 7 = 0.829 ...

-4.6 / - 5.8 = 0.793 ...

The second sequence is not a geometric sequence (it is an arithmetic sequence with a common difference of 1.2).