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**Writing Algebraic Expressions**

Lesson 2-3

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**Word phrases can be written as algebraic expressions.**

Use the words to determine what operation you are using. Use a variable for the phrase “a number.”

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Adding Phrases Plus More than Sum Increased by Added to Total

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**Subtracting Phrases Minus Difference of Subtracted from Decreased by**

Less than Less

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**Multiplying Phrases Dividing Phrases Times Product of Multiply Twice**

Divided by Quotient Into ratio

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**Example: 7 decreased by b**

“Decreased by” means subtract. 7 - b

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**Example: The product of 19 and k**

“Product” means multiply. We show multiplication by placing the factor right next to the variable. 19k

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Less than, more than Some word phrases contain the words “less than” or “more than.” When you see those words, start with the second part of the phrase. Example: 23 less than m m - 23

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**Example: 32 less than 5 times c**

The 32 is less than the 5 times c, which means we subtract 32 from the 5 times c. So, start with 5 times c. 5c - 32

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Tables When you are given a table of values, determine how to get from the first column to the second column. Describe that pattern with an algebraic expression.

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Example n ? 3 12 7 28 11 44

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**Compare from left to right.**

How do we get from 3 to 12? Add 9 or multiply by 4. How do we get from 7 to 28? Multiply by 4. If we multiply 11 by 4, we get 44. The pattern is to multiply our number, n, by 4. The algebraic expression to describe this is: 4n

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**Describing Unknown Numbers**

When you don’t know what a number is, let a variable stand for that number. Use an algebraic expression to describe what you’re looking for.

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Example Write an algebraic expression to describe Jerry’s age. Use the following information: Jerry is 4 years younger than his brother Steve. First, we have to know how old Steve is. We do not have an age for Steve, so we will use a variable: Let s = Steve’s age. Now that we have determined Steve’s age (s), we can use it to determine Jerry’s age. Jerry is 4 years younger than Steve. s - 4

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**If Steve is 22 years old, then how old is Jerry?**

Jerry is 18 years old. 22 - 4 18

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Homework Time

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