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Writing Algebraic Expressions

Writing Algebraic Expressions. Lesson 2-3. 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. ”. Adding Phrases. Plus More than Sum Increased by. Subtracting Phrases. Minus Difference

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Writing Algebraic Expressions

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  1. Writing Algebraic Expressions Lesson 2-3

  2. 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.”

  3. Adding Phrases • Plus • More than • Sum • Increased by

  4. Subtracting Phrases • Minus • Difference • Subtracted from • Decreased by • Less than

  5. Multiplying Phrases • Times • Product of Dividing Phrases • Quotient • Divided by

  6. Example: 7 decreased by b “Decreased by” means subtract. 7 - b

  7. Example: The product of 19 and k “Product” means multiply. We show multiplication by placing the factor right next to the variable. 19k

  8. 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

  9. 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

  10. 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.

  11. Example n ? 3 12 7 28 11 44

  12. 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

  13. 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.

  14. 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

  15. If Steve is 22 years old, then how old is Jerry? s - 4 Jerry is 18 years old. 22 - 4 18

  16. Homework Time

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