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