Question

The sum of n,2n,3n terms of an AP are S1,S2,S3 proce that S3=3(S2-S1)

Answer 1

S3=3/2(2a+2d)
=3(a+d)
3(S2-S1)
3(2/2(2a+d)-a)
3(a+d)
LHS=RHS

Answer 2

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