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.3. Complete all 20 problems.4. If you have questions, please come to me one at a time.5. Homework: Translating Algebraic

Expressions Worksheet