Maths Class 11 Chapter 9. Sequences and Series | Page 10

Sum of Special Series

Sn = 1 + 2 + 3 + … + n, then Sn = n( n + 1)/ 2

Sn = 1 2 + 2 2 + 3 2 + … + n 2, then Sn = n( n + 1)( 2n + 1)/ 6

Sn = 13 + 23 +...+ n3, then Sn = [ n( n + 1)] 2 / 4