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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 Times Product of Multiply Twice Of Dividing Phrases 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?

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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 Jerrys 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 = Steves age. Now that we have determined Steves age (s), we can use it to determine Jerrys 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? s Jerry is 18 years old.

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Homework Time

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