Algebraic Expressions An algebraic expression uses a letter, or variable, to stand for one or more unknown numbers. Mathematical symbols are often used to translate word phrases into algebraic expressions.

Algebraic Expressions Certain word phrases are associated with each operation. +….Sum of, increased by, more than -…..Difference of, decreased by, less than X….Product of, multiplied by, twice /.…Quotient of, divided by, ratio

Algebraic Expressions Let n represent the number: Example 1: 6 more than twice a number 2 x n + 6 or 2n + 6 Example 2: 18 less than half a number 1 x n – 18 or 1n – 18 2 2

Translate an Algebraic Expression Write a word phrase for the algebraic expression. A. 3(n – 5) 3 times the difference of a number minus 5 B. R + 8 The sum of a number and 3 8 divided by 3

Evaluating Expressions and Formulas To evaluate an expression, first replace the variable by a given value. Then simplify. Ex. 1 Evaluate 4x + 7 for x = 5 Step 1: Replace x with 5 4(5) + 7 Step 2: Simplify 20 + 7 = 27

Evaluating Expressions and Formulas Sometimes there is more than one variable in an expression. Example 2: Evaluate 2a + b for a = 2, b = 5 and c = 3 c Step 1: Replace a with 2, b with 5 and c with 3 2 x 2 + 5 3 Step 2: Simplify. 4+5 = 9 = 3 3 3

Practice Exercises 1. Take out a sheet of paper and number 1-20 2. Write your name, date, and # on the right hand side of paper. Complete all 20 problems. 4. If you have questions, please come to me one at a time. Homework: Translating Algebraic Expressions Worksheet