1. Learn to identify and evaluate expressions.

2. Vocabulary
variable
constant
algebraic expression

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

4. 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
 5
To evaluate an algebraic expression, substitute a number for the variable and then find the value.

5. Additional Example 1A: Evaluating Algebraic Expressions
Evaluate the expression to find the missing values in the table. y
5  y 6 7 10 30
Substitute for y in 5  y.
y = 6; 5  6 = 30
y = 7; 5 x 7= 35 35 50
y = 10; 5  10 = 50
The missing values are 35 and 50.

6. Additional Example 1B: Evaluating Algebraic Expressions
Evaluate the expression to find the missing values in the table. z
z  5 20 45 60 4
Substitute for z in z  5.
z = 20; 20  5 = 4 9
z = 45; __  5 = __ 45 9 12
z = 60; __  5 = __ 60 12
The missing values are 9 and 12.