If SP denotes the sum of the series 1+rp+r2p+…. to ond Sp denotes the sum of the series 1−rp+r2p−r3p+….to∞,|r|<1, then Sp+sp in terms of S2p is
2S2p
0
12S2p
-12S2p
SP=11−rp,sp=11+rp,S2p=11−r2p
Clearly, SP+sp=21−r2p=2S2p