Given sequences :
–2, –4, –6, –8, –10,...
16, –8, 4, –2, 1 , ......
–15, –18, –21.6, –25.92, –31.104, …
4, 10.5, 17, 23.5, 30, …
625, 125, 25, 5, 1, ….
Let us find the ratios.
–2, –4, –6, –8, –10,...
First sequence is just being decreased by -2. So it would be an Arithmetic sequence.
16, –8, 4, –2, 1 , ......
16/-8 = -2 and 4/-2 = -2.
In second sequence we got common ratio -2. Therefore, it's a geometric sequence.
–15, –18, –21.6, –25.92, –31.104, …
-15/-18 = 0.833
–21.6/ -18 = 0.833.
In second sequence we got common ratio 0.833. Therefore, it's a geometric sequence.
4, 10.5, 17, 23.5, 30, …
10.5/4 ≠ 17/10.5
Ratios are not same. So, it's not a geometric sequence.
625, 125, 25, 5, 1, ….
125/625 = 0.2 = 25/125.
<h3>In fourth sequence we got common ratio 0.2. Therefore, it's a geometric sequence.</h3>
