Which of the following sequences are in G.P.? (v) 1, −5, 25, −125,…

Which of the following sequences are in G.P.?

(v)  1, −5, 25, −125,…

Solution :

First term (a)  = 1/3, common ratio

r  = t2/t1   =  -5/1 r  = -5

r  = t2/t1   =  25/(-5) r = -5

Since the common ratios are same, it is geometric sequence.