Grade 12th passAlgebraFind the sum of 1.2+3.4+5.6+7.8+.................................................................. sudhanshu Tripathi 8 Years agoGrade 12th pass
Shailendra Kumar Sharma8 Years agoTr= (2r-1)(2r+2)Tr = 4r2 +4r-2r-2Tr= 4r2+2r-2So Sn = Sn= 4{n(n+1)(2n+1)/6} +2 {n(n+1)}/2 -2n =2/3{n(n+1)(2n+1)+ n(n+1)-2n