4 Find the infinite sum of the geometric sequence with a = 2, r T-- if it exists.

Algebra and Trigonometry (6th Edition)
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ISBN:9780134463216
Author:Robert F. Blitzer
Publisher:Robert F. Blitzer
ChapterP: Prerequisites: Fundamental Concepts Of Algebra
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Problem 1MCCP: In Exercises 1-25, simplify the given expression or perform the indicated operation (and simplify,...
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Find the infinite sum of the geometric sequence with a = 2, r° = 4 - if it exists
**Finding the Infinite Sum of a Geometric Sequence**

Given:
- Initial term (a): \(2\)
- Common ratio (r): \(\frac{4}{5}\)

We are required to find the infinite sum \(S_\infty\) of the geometric sequence if it exists.

The formula for the infinite sum of a geometric sequence \(S_\infty\) is given by:

\[ S_\infty = \frac{a}{1 - r} \]

where \(|r| < 1\) for the series to converge.

### Applying the Formula

1. **Identify the values:**
   - \( a = 2 \)
   - \( r = \frac{4}{5} \)
   
2. **Check the condition for convergence:**
   - Since \(\left|r\right| = \left|\frac{4}{5}\right| = 0.8\), which is less than 1, the series converges.

3. **Substitute into the formula:**

   \[ S_\infty = \frac{2}{1 - \frac{4}{5}} \]

4. **Compute the sum:**

   \[ S_\infty = \frac{2}{\frac{1}{5}} \]

   \[ S_\infty = 2 \times 5 \]

   \[ S_\infty = 10 \]

Thus, the infinite sum \( S_\infty \) is \( \boxed{10} \).

*[Note: Insert a box for student input alongside the computed formula as shown in the original prompt to help with practicing calculations.]*

### Interface Elements
- **Add Work:** This button could allow students to show their step-by-step solution or computation to arrive at the sum.
- **Next Question:** This button could lead students to the subsequent problem for further practice.
Transcribed Image Text:**Finding the Infinite Sum of a Geometric Sequence** Given: - Initial term (a): \(2\) - Common ratio (r): \(\frac{4}{5}\) We are required to find the infinite sum \(S_\infty\) of the geometric sequence if it exists. The formula for the infinite sum of a geometric sequence \(S_\infty\) is given by: \[ S_\infty = \frac{a}{1 - r} \] where \(|r| < 1\) for the series to converge. ### Applying the Formula 1. **Identify the values:** - \( a = 2 \) - \( r = \frac{4}{5} \) 2. **Check the condition for convergence:** - Since \(\left|r\right| = \left|\frac{4}{5}\right| = 0.8\), which is less than 1, the series converges. 3. **Substitute into the formula:** \[ S_\infty = \frac{2}{1 - \frac{4}{5}} \] 4. **Compute the sum:** \[ S_\infty = \frac{2}{\frac{1}{5}} \] \[ S_\infty = 2 \times 5 \] \[ S_\infty = 10 \] Thus, the infinite sum \( S_\infty \) is \( \boxed{10} \). *[Note: Insert a box for student input alongside the computed formula as shown in the original prompt to help with practicing calculations.]* ### Interface Elements - **Add Work:** This button could allow students to show their step-by-step solution or computation to arrive at the sum. - **Next Question:** This button could lead students to the subsequent problem for further practice.
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