# [2] – Geometric Sequence 等比數列

00:05 – concept and general term of geometric sequence 等比數列的概念與通項
04:00 – properties of geometric sequence 等比數列的性質
07:35 – illustrative example 1 例子 1
08:16 – illustrative example 2 例子 2
10:43 – illustrative example 3 例子 3

[高中數學] – Arithmetic and Geometric Sequences 等差與等比數列

Category: S4-S6 Algebra

• Rzc

in 14:11, the equation $1000*1.03^n$ is $equals ar^(n-1)$ ?

• rzc

你好,我想問 $2/3*3^-1$ 為什麼能寫$2/3(1/3)^n-1 ?$ 因為我看到$3^-n= 1/3^n$ ,但為什麼指數無-(n-1)? thanks

• rzc

為什麼$2/(3*3^(n-1))=(2/3)*(1/3)^(n-1)$?

• Rzc

in 3:41, why $2/(3*3^(n-1))$ equals $(2/3)*(1/3)^(n-1)$ ? as i know, $3^-a = 1/3^a$ . sorry, i am noob in math. i don’t understand.

\large \begin{aligned} \frac{2}{3^n} &= \frac{2}{3\times 3^{n-1}} \\\\ &= \frac{2}{3} \times \frac{1}{3^{n-1}} \\\\ &= \frac{2}{3} \times \frac{1^{n-1}}{3^{n-1}} \ \ \ \because 1^{n-1}=1 \\\\ &= (\frac{2}{3})(\frac{1}{3})^{n-1} \end{aligned}