the sum of n terms of a series is a.2^n-b, find its n th term. are the term s of this series in g.p.?

Answer 1

If r = 2,
Sn = a*(2^(n-1)-1)
so, if b = a, it could be a gp

a,2a,4a,8a,...2^(n-1)*a
Sn = a(1+2+...+2^(n-1))
= a(2^n-1) = a*2^n-a

Answer 2

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