Chapter 1: Sequences and Series
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4. 1.4 Geometric Series
Objectives:
- Derive a rule for determining the sum of n terms of a geometric series.
- Determine the first term, the common ratio, the number of terms, or the value of the sum of a specific number of terms in a problem involving a geometric series.
A Geometric Series is the expression for the sum of terms of a Geometric Sequence.
Again, the common ratio and general term will be the same for the corresponding sequence.
The sum of a Geometric Sequence can be shown to be
Sn =\( \frac{t_1(r^n - 1)}{r - 1} \), \( r \neq 1 \) and Sn = \( \frac{t_1r^n - t_1}{r - 1} \), \( r \neq 1 \)
Example:
For the Geometric Series 4 + 8 + 16 + 32 + 64 + ...
S8 = \( \frac{4(2^8 - 1)}{1} \)