# Lecture-10

Play Video
 NCERT EXERCISE 9.4

Find the sum to n terms of each of the series in Exercises 1 to 7.

Question 1. $1\times2+2\times3+3\times4+4\times5+…$

Question 2. $1\times2\times3+2\times3\times4+3\times4\times5+…$

Question 3. $3\times1^2+5\times2^2+7\times3^2+…$

Question 4. $\frac{1}{1\times2}+\frac{1}{2\times3}+\frac{1}{3\times4}+…$

Play Video
 NCERT EXERCISE 9.4

Find the sum to n terms of each of the series in Exercises 1 to 7.

Question 5. $5^2+6^2+7^2+…+20^2$

Question 6. $3\times8+6\times11+9\times14+…$

Question 7. $1^2+(1^2+2^2)+(1^2+2^2+3^2)+…$

Find the sum to n terms of the series in Exercises 8 to 10 whose nth terms is given by

Question 8. $n(n+1)(n+4)$

Question 9. $n^2+2^n$

Question 10. $(2n-1)^2$