Question
If S1, S2 and S3 be respectively the sums of n, 2n and 3n terms of a GP., prove that S1 (S3 – S2) = (S2 – S1)2
Solution
Let a be the first term and r be the common ratio of a G.P.
...(i)
...(ii)
...(iii)
L.H.S. =
=
R.H.S. =
=
∴ L.H.S. = R.H.S.
Hence,