Given: The sum of first three terms of a GP is 13/12 and their product is - 1.
Let
,a,ar be the first three terms of the given GP.
⇒+a+ar= .......(1)
⇒.a.ar=−1 .........(2)
From
(2), we get
a3=−1⇒a=−1 By substituting a = - 1 in equation (1), we get
⇒−−1−r= ⇒12r2+25r+12=0 ⇒ r = - 4/3 or r = - 3/4
Case 1: When a = - 1 and r = - 4/3
Then these three terms are: 3/4, - 1, 4/3
Case 2: When a = - 1 and r = - 3/4
Then these three terms are: 4/3, - 1, 3/4
Hence, in either case these three are: - 1, 3/4, 4/3