# Geometric Progression

## Basic Algebra Review Part 5: Geometric Progression (Tagalog)

Formulas:

• The common ratio:
$r = \dfrac{a_2}{a_1} = \dfrac{a_3}{a_2} = \dfrac{a_4}{a_3} = ~ ...$
• The nth term:
$a_n = a_m r^{n - m}$
• Sum of the first n terms
$S_n = \dfrac{a_1(r^n - 1)}{r - 1}$ for $n \gt 1$

$S_n = \dfrac{a_1(1 - r^n)}{1 - r}$ for $n \lt 1$

Note for Calculator
The STAT mode of calulator y = a · b^x cannot be used for r < 0.

• Mathematics inside the configured delimiters is rendered by MathJax. The default math delimiters are $$...$$ and $...$ for displayed mathematics, and $...$ and $...$ for in-line mathematics.