# Learn How to Express Sums in Summation Notation | Summary and Q&A

4.2K views
April 9, 2021
by
The Math Sorcerer
Learn How to Express Sums in Summation Notation

## TL;DR

This video explains how to write sums using summation notation, demonstrated through various examples.

## Questions & Answers

### Q: What does the Greek letter sigma represent in summation notation?

The Greek letter sigma represents "add up" in summation notation. It is used to indicate that the terms within the sum need to be added together.

### Q: Can any variable be used in summation notation?

Yes, any variable can be used in summation notation, except for the variable being summed. Conventionally, variables like i, j, and k are commonly used, but any letter can be chosen.

### Q: How do you write a sum with multiple terms in summation notation?

To write a sum with multiple terms in summation notation, you can group the terms within parentheses and use a different variable for each term. For example, a sub i plus b sub i can be expressed as sigma(a sub j + b sub j) from j = 1 to 10.

### Q: What if the sum involves multiplying variables?

If the sum involves multiplying variables, you can use subscripts to differentiate the variables. For example, f sub i times x sub i squared can be expressed as sigma(f sub k times x sub k squared) from k = 1 to 8.

## Summary & Key Takeaways

• The video teaches how to write sums in summation notation, using the Greek letter sigma to represent "add up."

• Examples are provided to show how to write different types of sums using different variables, such as x, a, b, f, and y.

• The video explains how to start and end the summation, and how to express the terms within the sum.