Solve Infinite Series: Sum of -(5/4)^n

In summary, an infinite series is a sum of infinitely many terms determined by a pattern or rule. To solve it, one needs to identify the pattern and use a specific formula, such as the geometric series formula. The common ratio in this infinite series is -(5/4), making the sum finite. Real-life applications of infinite series include finance, physics, and computer science. For instance, compound interest, motion of a pendulum, and algorithms all involve infinite series.
  • #1
NIZBIT
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[SOLVED] Infinite series help

Homework Statement



[tex]\sum- (\frac{5}{4})^n[/tex]
i=infinity and n=0

Homework Equations


Convergence of a geometric series
[tex]\sum (ar)^n = a/(1-r) when 0<|r|<1[/tex]

The Attempt at a Solution


I have to explain why this series diverges or converges. The test for divergence gives an answer of infinity so it diverges. The terms are 1, -5/4, 25/16, -125/64, 625/256... To me it looks like a geometric series with r=|-5/4| which diverges because |-5/4|[tex]\geq[/tex] 1. Is this correct?
 
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  • #2
Correct.
 
  • #3
thanks!
 

Related to Solve Infinite Series: Sum of -(5/4)^n

1. What is an infinite series?

An infinite series is a sum of infinitely many terms. Each term is determined by a pattern or rule, and the series can either have a finite sum or diverge (not have a finite sum).

2. How do you solve an infinite series?

To solve an infinite series, you need to identify the pattern or rule that determines each term and use a specific formula or method to find the sum. In this case, we use the formula for a geometric series: S = a / (1-r), where a is the first term and r is the common ratio.

3. What is the common ratio in this infinite series?

The common ratio in this infinite series is -(5/4). This means that each term is multiplied by -(5/4) to get the next term.

4. Is the sum of this infinite series finite or infinite?

The sum of this infinite series is finite. Using the formula for a geometric series, we can calculate the sum as follows: S = (-5/4) / (1-(-5/4)) = (-5/4) / (1+5/4) = (-5/4) / (9/4) = -5/9. Therefore, the sum is a fraction and not infinite.

5. Can you provide an example of a real-life application of infinite series?

Infinite series have many real-life applications, including in finance, physics, and computer science. For example, in finance, the concept of compound interest can be represented as an infinite series. In physics, infinite series can be used to describe the motion of a pendulum or the expansion of a gas. In computer science, infinite series are used in algorithms and data structures.

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