📚 What is a Geometric Series?
A geometric series is the sum of the terms of a geometric sequence. Each term in the sequence is multiplied by a constant, called the common ratio, to get the next term.
♾️ Definition of an Infinite Geometric Series
An infinite geometric series is a geometric series with an infinite number of terms. It continues without end.
🛑 Definition of a Finite Geometric Series
A finite geometric series is a geometric series with a limited number of terms. It has a definite start and end.
📊 Infinite vs. Finite Geometric Series: A Detailed Comparison
| Feature |
Infinite Geometric Series |
Finite Geometric Series |
| Number of Terms |
Infinite |
Finite |
| Sum |
May converge to a finite value (if |r| < 1) or diverge. |
Always has a finite sum. |
| Common Ratio (r) |
Convergence depends on the value of 'r'. If $|r| < 1$, the series converges. |
The value of 'r' does not affect the finiteness of the sum. |
| Formula for Sum |
If $|r| < 1$: $S = \frac{a}{1-r}$, otherwise, the sum diverges. |
$S_n = \frac{a(1-r^n)}{1-r}$, where 'n' is the number of terms. |
| Examples |
$1 + \frac{1}{2} + \frac{1}{4} + \frac{1}{8} + ...$ |
$1 + 2 + 4 + 8 + 16$ |
🔑 Key Takeaways
- ♾️ Infinite Series: An infinite geometric series goes on forever and its sum may converge to a specific number only when the absolute value of the common ratio is less than 1 ($|r| < 1$).
- 🔢 Finite Series: A finite geometric series has a set number of terms, so you can always find its sum using the appropriate formula, regardless of the common ratio.
- ➗ Convergence: Convergence is a crucial concept for infinite geometric series. A series *converges* if its sum approaches a finite value as you add more terms. Otherwise, it *diverges*.