If Sp denotes the sum of the series 1+rp+r2p+....... to ∞ and sp denotes the sum of the series 1−rp+r2p−r3p+....... to ∞,|r|<1 then Sp+sp is
If Sp denotes the sum of the series 1+rp+r2p+.... to ∞ and sp the sum of the series 1−rp+r2p− ....to ∞, prove that Sp+sp=2S2p.