等比數列求和 (有限項) | Summation of a Geometric Sequence (Finite Number of Terms)

影片內容：

00:40 – 等比數列求和公式 | derivation of the summation formula of geometric sequence
03:30 – 例子 1 | example 1
06:07 – 例子 2 | example 2
10:25 – 例子 3 | example 3