# Sequences and Series Class 11 Lecture 9

“The Effective Leader Recognizes That They Are More Dependent On Their People Than They Are On Them. Walk Softly.”

# Lecture - 9 Chapter 9 Sequences & Series

Introduction to Special Series,
Sum of first n natural numbers
$1+2+3+…+n=\frac{n(n+1)}{2}$

Inspirational Story of Mathematician Gauss when he was in elementary school told by Prof. Arvind Gupta

Sum of Squares of first n natural numbers
$1^2+2^2+3^2+…+n^2=\frac{n(n+1)(2n+1)}{6}$

Sum of Cubes of first n natural numbers
$1^3+2^3+3^3+…+n^3= \left ( \frac{n(n+1)}{2} \right )^2$