Answer:
The first two are arithmetic sequences
Explanation:
-20 , -25,-30,-35,-40,.....
If we subtract 5 from each term we get the next
This is an arithmetic sequence, with a common difference of -5
-15.6, -12.9, -10.2, -7.5,-4.8.....
If we add 2.7 to each term we get the next
This is an arithmetic sequence, with a common difference of 2.7
3.1, 6.2,12.4,24.8,49.6
We multiply by 2 to get the next term
This is a geometric sequence with a common ratio of 2
7.2,3.6,1.8,.9,.45
We multiply by .5 to get the next term
This is a geometric sequence with a common ratio of .5