Question

This is from the chapter sequence and series​

Answer 1

Step-by-step explanation:

The nth term in this series is equal to (n²+n)

Sum of all terms in this series

= (1²+2²+....+n²)+(1+2+....n)

= $\frac{n(n + 1)(2n + 1)}{6} + \frac{n(n + 1)}{2}$

= $\frac{n(n + 1)(n + 2)}{3}$