math
posted by Mark .
A sequence has t(sub1) = 5 and t(sub2) = 15
a. if the sequence is geometric, what is the common ratio? What do t(sub3) and t(sub4) equal?
b. if the sequence is arithmetic, what is the common ratio? What do t(sub3) and t(sub4) equal?

a. r=3, so you have 5,15,45,135,...
b. d=10, do 5,15,25,35,...