NCERT Class 11 Mathematics Solutions: Chapter 9 – Sequences and Series Miscellaneous Exercise 9 Part 12 (For CBSE, ICSE, IAS, NET, NRA 2023)

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Formulae for Arithmetic Series

1. Find the 20th term of the series terms.


The given series is terms


So, the term of the series is .

2. Find the sum of the first n terms of the series:


The given series is

On subtracting both the equations, we obtain