Geometric Sequences

Is this a Geometric Sequence?

100

−4,−8,−16,...

Yes

200

5,10,12,15,...

No

300

2,4,6,8,...

No

400

22,−44,88,−176,...

Yes

500

7,−56,448,−3584,...

Yes

What is the ratio?

100

1, 3, 9, 27...

3

200

4, 8, 16, 32....

2

300

13, 39, 117, ... 

3

400

12, 84, 588,....

7

500

12, -60, 300.....

-5

Next three terms

100

an = 4 • -6^n-1

4, -24, 144

200

a_n = 2ⁿ

2, 4, 8

300

a_n= 5 • 6^n-1

5, 30, 180

400

a_n=2^n-1

1, 2, 4

500

a_n=-4((-2)^n-1)

-4, 8, -16