Question

The sum of first n, 2n and 3n terms of an A.P. are S1, S2, and S3, respectively.
Prove that S3 = 3(S2-S1)​

Answer 1

Answer:

S2=5,S1=2=5-2=3.So, therefore S3=3(S2-S1)

Answer 2

plz refer to this attachment