Question 72205
Find the missing geometric sequence 15, __ , 81,...
 
the missing term is (t2/t1)=(t3/t2)
                  => (t2/15)=(81/t2)
                  =>  (t2)^2 = 81 * 15
                  =>   t2 = 9 sqrt(15).

Find the missing geometric sequence 36, __ , 100, ... 

the missing term is (t2/t1)=(t3/t2)
                  => (t2/36)=(100/t2)
                  =>  (t2)^2 = 100 * 36
                  =>   t2 = 10 * 6 = 60 .