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If Sn represents the sum of n terms of a...

If `S_n` represents the sum of n terms of a G.P. whose first term and common ratio are a and r respectively. Prove that :
`S_1 +S_2+S_3+.....+S_(m)= (am)/(1-r)-(ar(1-r^(m)))/((1-r)^2)`.

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