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

Warm Up Simplify. 1. 4 + 7  3  1 2. 87  15  5 3. 6(9 + 2) + 7 4. 35  7  5

 Problem of the Day How can the digits 1 through 5 be arranged in the boxes to make the greatest product? 

Learn to identify and evaluate expressions.

Vocabulary variable constant algebraic expression

A variable is a letter or symbol that represents a quantity that can change. A constant is a quantity that does not change.

Algebraic Expressions NOT Algebraic Expressions 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 + y 85 ÷ 5 35  w + z 10 + 3  5 To evaluate an algebraic expression, substitute a number for the variable and then find the value.

Additional Example 1A: Evaluating Algebraic Expressions Evaluate the expression to find the missing values in the table. y 5  y 16 27 35 80 Substitute for y in 5  y. y = 16; 5  16 = 80 y = 27; 5  = 27 y = 35; 5  = 35 The missing values are 135 and 175.

Additional Example 1B: Evaluating Algebraic Expressions Evaluate the expression to find the missing values in the table. z z  5 + 42 20 45 60 Substitute for z in z  5 + 42. z = 20; 20  5 + 16 = 20 z = 45; __  5 + 16 = __ 45 z = 60; __  5 + 16 = __ 60

Check It Out: Example 1A Evaluate the expression to find the missing values in the table. x x  9 18 36 54 2 Substitute for x in x  9. x = 18; 18  9 = 2 x = 36;  9 = 36 x = 54;  9 = 54

Check It Out: Example 1B Evaluate the expression to find the missing values in the table. z 8  z + 23 7 9 11 64 Substitute for z in 8  z + 23. z = 7; 8  7 + 8 = 64 z = 9; 8  __+ 8 = __ 9 z = 11; 8  __ + 8 = __ 11

You can write multiplication and division expressions without using the symbols  and . Instead of . . . You can write . . . x  3 x  3 x(3) 3x 35 y 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

Additional Example 2: Evaluating Expressions with Two Variables A rectangle is 4 units wide. How many square units does the rectangle cover if it is 3, 4, 5, or 6 units long? Make a table to help you find the number of square units for each length. l w l x w 3 4 12 5 6 3 x 4 = square units 4 x 4 = square units 5 x 4 = square units 6 x 4 = square units

l w l x w Check It Out: Example 2 A rectangle is 3 units wide. How many square units does the rectangle cover if it is 2, 3, 4, or 5 units long? Make a table to help you find the number of square units for each length. l w l x w 2 3 6 4 5 2 x 3 = square units 3 x 3 = square units 4 x 3 = square units 5 x 3 = square units

1. Evaluate the expression to find the missing values in the table. l Lesson Quiz x x2 – 5 10 7 5 1. Evaluate the expression to find the missing values in the table. l w l x w 2 6 3 4 5 2. A rectangle is 6 units wide. How many square units does the rectangle cover if it is 2, 3, 4, or 5 units long?