The G.P. is x 3 , x 5 , x 7 ,…
Let the first term and common ratio of the given G.P. be a and r respectively.
Here,
a= x 3 r= x 5 x 3 = x 2
Here, r>1
The formula for the sum of first n terms of a G.P. for r>1 is given by,
S n = a( r n −1 ) r−1
Substitute the values of a and rin equation (1) to obtain the n th term.
S n = x 3 ( ( x 2 ) n −1 ) ( x 2 )−1 = x 3 ( x 2n −1 ) x 2 −1
Thus, the sum of n terms of the G.P. x 3 , x 5 , x 7 ,… is x 3 ( x 2n −1 ) x 2 −1 .