1. Ch 1.1 - Variables in Algebra Objective: To recognize and evaluate variable expressions and basic formulas.

2. Definitions Variable A letter that is used to represent a number is known as a variable. For example: In the expression “5x”, x is a variable representing a number that is multiplied by 5

3. What is a variable? A variable represents an unknown value. 1) 3 + ___ = 10 2) 6 + = 9 3) 8 + x = 12 4) 5 + = 8 These are all variables

4. Variable Expressions Variable expressions consist of constants, variables, and operations. ExampleMeaningOperation

5. 18 3 2(4 + 5) Evaluate the expression if a = 3, b = 4, and c = 5 1) ab - c 2) 2a(b - c) 3) 4) (3)(4) - 5 12 - 5 7 2(3)(4 - 5) 2(3)(-1) -6 2(3) + 4 2 6 + 4 2 6 + 2 = 8 3 2(9) 3 == 6