20.3 Arithmetic series
Arithmetic series
An arithmetic series is the sum of an arithmetic sequence. In this lesson, we will learn how to solve problems using the arithmetic series formula.
Basic concepts:
 Arithmetic sequences
Lessons
Notes:
• the sum of $n$ terms of an arithmetic series:
${s_n}$= $\frac{n}{2}[2{t_1} + (n  1)d]$
= $\frac{n}{2}[{t_1} + {t_n}]$

3.
$t_{n}=s_{n}s_{n}1$
The sum of the first n terms of an arithmetic series is ${s_n} = 7{n^2}  5n$ .