Modelling with Sequences & Series (Edexcel A-Level Mathematics): Quizzes

Common difference

$a_n = a_1 + (n-1)d$

$S_n = \frac{n}{2}(2a_1 + (n-1)d)$

Multiplying by a constant

$a_n = a_1 r^{n-1}$

$S_n = \frac{a_1(1-r^n)}{1-r}$

$|r| < 1$

6400

$90 + 10n$

£42,500