Finite Geometric Series (Grade 12 NSC Matric Mathematics): Quizzes

Sum of specific number of geometric terms

Multiply by the common ratio

The first term

First term already represents $r^0 = 1$

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

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

$r \neq 1$

$n \times a$

Alternating positive and negative terms

$r = \frac{T_2}{T_1}$