1. Is the sequence geometric? If so, identify the common ratio.

6, 12, 24, 48, ...

yes; 2

yes, - 2

yes; 4

no

2. What is the fifth term of the geometric sequence?

5, 15, 45, ...

1,215

1,875

405

3,645

1) yes; 2 6*2=12 12*2=24 24*2=48

2) Next Term (or nth term) = ar^n-1

a = first term, i. e. 5

r = common ratio i. e. 3 (as 15/5=3 and 45/15=3

n = ...

as you already have 1st, 2nd and 3rd terms

substituting now

T4 = ar^n-1

= 5*3^4-1

= 5*3^3

= 5*27

T4 = 135

T5 = ar^n-1

= 5*3^5-1

= 5*3^4

= 5*81

T5 = 405