Geometric sequence

Question

which of these sequences is geometric

-18,-12,-6,0

1/2,1/4,1/4,1/5

3,-1,-5,-9

3/2,-1/2,1/6,-1/18

4,9,16,25

Answer 1

To find a geometric sequence take the 2nd term and divide by the 1st term. Then take the 3rd term and divide by the 2nd term. Do you get the same number? If so, try the 4th term divided by the 3rd term. Do you get the same number as the other two?

If you get the same number dividing each consecutive pair of terms, then it's a geometric sequence.

Example:

For -18, -12, -6, 0:

-12/-18 = 1/3

-6/-12 = 1/2

Not a geometric sequence