Arithmetic Series (Leaving Cert Mathematics): Flashcards

The sum of the terms of an arithmetic sequence

Sequence lists numbers; series adds them together

Sum of the first $n$ terms of a series

The first term

Common difference between consecutive terms

The $n$th individual term

$S_n = \frac{n}{2}[2a + (n-1)d]$

$T_n = S_n - S_{n-1}$

Number of terms we want to add

Identify $a$ and $d$

Disregard them; $n$ must be positive

Average of first and last terms × number of terms