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 

Indoraptor for sure