Suppose a series of `n` terms given by `S_(n)=t_(1)+t_(2)+t_(3)+`. . . .`+t_(n)`
then `S_(n-1)=t_(1)+t_(2)+t_(3)+`. . . .`+t_(n-1),nge1` subtracting we get `S_(n)-S_(n-1)=t_(n),nge2` surther if we put `n=1` is the first sum then `S_(1)=t_(1)` thus w can write `t_(n)=S_(n)-S_(n-1),nge2` and `t_(1)=S_(1)`
Q. The sum of `n` terms of a series is `a.2^(n)-b`. where a and b are constant then the series is

Options

A. A.P
B. G.P
C. A.G.P
D. G.P from second term onwards

Answer

D