Question 9 - Chapter 9 Class 11 Sequences and Series (Important Question)

Last updated at April 16, 2024 by

Ex 9.4, 9 - Find sum of series, nth term is n2 + 2n - Class 11 - Finding sum from nth number

Ex 9.4, 9 - Chapter 9 Class 11 Sequences and Series - Part 2
Ex 9.4, 9 - Chapter 9 Class 11 Sequences and Series - Part 3

Go Ad-free

Transcript

Question 9 Find the sum to n terms of the series whose nth terms is given by n2 + 2n Given an = n2 + 2n Now, sum of n terms is Now, = 2 + 4 + 8 + + 2n This is GP with first term A = 2 & common ratio R = 4/2 = 2 We know that sum of n term in GP Sn = ( (R^n 1))/(R 1) Putting values Now from (1) Putting values = (n(n+1)(2n+1))/6 + 2(2n 1) Thus, the required sum is (n(n+1)(2n+1))/6 + 2(2n 1)

Davneet Singh's photo - Co-founder, Teachoo

Made by

Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo