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.

An algebraic expression contains one or more variables and may contain operation symbols. So p 7 is an algebraic expression.

2-1 Variables and Expressions

Course 1

Algebraic Expressions NOT Algebraic Expressions

150 + y 85 ÷ 5

35 w + z 10 + 3 5

2-1 Variables and Expressions

Course 1

Evaluate to find the missing values.

Substitute for y in 5 y.y 5 y

16

27

35

80 y = 16; 5 16 = 80

135

175

27 135

35 175

y = 27; 5 =

y = 35; 5 =

The missing values are 135 and 175.

2-1 Variables and Expressions

Course 1

Evaluate the expression to find the missing values in the table.

z z 5 + 42

20

45

60

20 z = 20; 20 5 + 16 = 20

z = 45; __ 5 + 16 = __

z = 60; __ 5 + 16 = __

25

28

45 25

60 28

The missing values are 25 and 28.

Substitute for z in z 5 + 42.

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) 3x

35y

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

2-1 Variables and Expressions

Course 1

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.

3 x 4 = square units

20

16

l w l x w

3 4 12

4 4

5 4

6 4The rectangle will cover 12, 16, 20, or 24 square units.

4 x 4 = square units

5 x 4 = square units

6 x 4 = square units

12

16

20

2424

2-1 Variables and Expressions

Course 1

1. Evaluate the expression to find the missing values in the table.

Lesson Quiz

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?

95

44

20

12

l w l x w2 6

3 6

4 6

5 6

18

24

30

x x2 – 5

10

7

5