# Writing a series in sigma notation | Summary and Q&A

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November 26, 2013
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Writing a series in sigma notation

## TL;DR

Learn how to express an infinite series using sigma notation by analyzing its terms and patterns.

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### Q: What is the purpose of expressing an infinite series in sigma notation?

Expressing an infinite series in sigma notation allows for a concise representation of the series, making it easier to describe and analyze its behavior.

### Q: How can the pattern of the oscillating sign (-1^n) be represented in sigma notation?

The pattern of the oscillating sign can be represented using (-1^n) within the sigma notation, where n is the index variable.

### Q: What is the pattern observed in the powers of 5 in the series?

The powers of 5 in the series follow a pattern where the index n corresponds to the exponent of 5 in each term. For example, 5 to the first power (5^1) corresponds to the term with n = 1.

### Q: How is the pattern of 3 multiplied by the index represented in sigma notation?

The pattern of 3 multiplied by the index can be represented as (3n) within the sigma notation, where n is the index variable.

## Summary & Key Takeaways

• The content discusses the process of expressing an infinite series in sigma notation.

• The series consists of terms with an oscillating sign (-1^n), powers of 5, and 3 multiplied by the index.

• By identifying the patterns in the terms, the series can be written in sigma notation as the sum of (-1^n * 5^n) / (3n).