1. 2-1 Variables and Expressions Course 1 Lesson Presentation Lesson Presentation Problem of the Day Problem of the Day 2-1 Variables and Expressions Course 1 Warm Up Warm Up

2. 2-1 Variables and Expressions Course 1 Learn to identify and evaluate expressions.

3. 2-1 Variables and Expressions Course 1 Vocabulary variable constant algebraic expression

4. 2-1 Variables and Expressions Course 1 A variable is a letter or symbol that represents a quantity that can change. A constant is a quantity that does not change.

5. 2-1 Variables and Expressions Course 1 An algebraic expression contains one or more variables and may contain operation symbols. So p  7 is an algebraic expression. Algebraic Expressions NOT Algebraic Expressions 150 + y85 ÷ 5 35  w + z 10 + 3  5 To evaluate an algebraic expression, substitute a number for the variable and then find the value by using the order of operations.

6. 2-1 Variables and Expressions Course 1 Evaluate the expression to find the missing values in the table. Additional Example 1A: Evaluating Algebraic Expressions Substitute for y in 5 y. y5 y 35 315 105 1050 205 20100

7. 2-1 Variables and Expressions Course 1 Evaluate the expression to find the missing values in the table. Additional Example 1B: Evaluating Algebraic Expressions z z + 4 2 20 45 60 36 z = 20; 20 + 16 = 36 z = 45; __ + 16 = __ z = 60; __ + 16 = __ 61 76 45 61 60 76 The missing values are 61 and 76. Substitute for z in z  5 + 4 2.

8. 2-1 Variables and Expressions Course 1 Check It Out: Example 1A Evaluate the expression to find the missing values in the table. Substitute for x in x  9. x x  9 18 36 54 2 x = 18; 18  9 = 2 4 6 4 54 6 x = 36;  9 = x = 54;  9 = 36 The missing values are 4 and 6.

9. 2-1 Variables and Expressions Course 1 Evaluate the expression to find the missing values in the table. Check It Out: Example 1B z 8 z + 2 3 7 9 11 64 z = 7; 8 7 + 8 = 64 z = 9; 8 __+ 8 = __ z = 11; 8 __ + 8 = __ 80 96 980 1196 The missing values are 80 and 96. Substitute for z in 8  z + 2 3.

10. 2-1 Variables and Expressions Course 1 You can write multiplication and division expressions without using the symbols  and . Instead of... You can write... x 3 x  3 35 ÷ y x(3) 3x3x 35 y When you are multiplying a number times a variable, the number is written first. Write “3x” not “x3.” Read 3x as “three x.” Writing Math