find the sum to n terms... 3.1^2 + 5.2^2 +7. 3^2...
Answers
Answered by
6
Sn = 3.1² + 5.2² + 7.2² +.......
Sn = (2.1 +1).1² + (2.2+1).2² + (2.3+1).3² +....
Sn = Sigma (2r +1).r² [ 1 ≤ r ≤ n ]
Sn = Sigma ( 2r³ + r²) [ 1 ≤ r ≤ n ]
Sn = 2.Sigma r³ + Sigma r² [ 1 ≤ r ≤ n ]
Sn = 2.{n(n+1)/2}² + n(n +1)(2n +1)/6
Sn = (2.1 +1).1² + (2.2+1).2² + (2.3+1).3² +....
Sn = Sigma (2r +1).r² [ 1 ≤ r ≤ n ]
Sn = Sigma ( 2r³ + r²) [ 1 ≤ r ≤ n ]
Sn = 2.Sigma r³ + Sigma r² [ 1 ≤ r ≤ n ]
Sn = 2.{n(n+1)/2}² + n(n +1)(2n +1)/6
Similar questions