Arithmetic Sequences & Series (Edexcel A-Level Mathematics): Flashcards

A constant difference between consecutive terms.

It is denoted by $a$.

$d$ denotes the common difference.

It is $a, a + d, a + 2d, ...$

$a_n = a + (n - 1)d$.

$S_n = n/2 * (2a + (n - 1)d)$.

$S_n = n/2 \cdot (a + a_n)$.

$a_5 = 3 + (5-1) \times 4 = 19$.

$n$ equals 5, the number of terms.

$S_n = n/2 * (2a + (n-1)d)$ where $a$ is the first term.