1. Chapter 1-1 Variables and expressions
Unit 1
Chapter 1-1 Variables and expressions

2. Numerical Expression Examples:
Vocabulary:
Expression-mathematical phrase that contains operations, numbers, AND/OR variables.
***Does not have an equal sign (=)
Variable – A letter that represents a value that can change or vary
2 types of expression:
Numerical Expression: Does not contain variables
Variable Expression: Contains one or more variables.
Numerical Expression Examples:
(5)
Variable Expressions Examples
𝑋 X+2
P-R N

3. Writing Variable Expression
Key Words: Total (+) Difference (-) Product (X) (•) () Quotient (÷) (-) (/) More Than (+) Fewer Than (-) Times (X) (•) () Divided By (÷) (-) (/) Increased By (+) Less Than (-) Decreased By (-)

4. Write the variable expression for the given word phrase:
Ex 1: Nine more than a number Y
Ex 2: Four less than a number N
Ex 3: Five times the quantity four plus a number C
(See next slide for answers)

5. Write the variable expression for the given word phrase:
Ex 1: Nine more than a number Y
9 + Y
Ex 2: Four less than a number N
N - 4
Ex 3: Five times the quantity four plus a number C
5 X (4+C) or 5(4+C)

6. Substitution Property of Equality
If two quantities are equal, then one quantity can be replaced by the other in a mathematical expression
“Plug it in Plug it in!”
Evaluate each expression if K = 2, m=7, and X = 4.
Ex 1: 6M-2K
6(7) – 2 (2) (replace m with 7 and K with 2)
Multiply
Subtract

7. Substitution Property of Equality
Example 2:
Evaluate each expression if K = 2, m=7, and X = 4.
= 𝐾𝑀 2 (Replace k with 2 and m with 7)
= 2 (7) 2 (Multiply numerator)
= (Divide fraction) =7
Example 3:
Evaluate each expression if K = 2, m=7, and X = 4.
=3X (Replace x with 4 )
=3(4) (Multiply 3 and 4)
= (Add)
=19

8. Let’s do some practice Evaluate: 3a – 5, A=10 2) 6𝑌 2 Y=2
3) 2X + 3Y + 4Z, X=4, Y=3, Z=2
(answers on next slide)

9. Let’s check our answers!
Evaluate:
3a – 5, A=10
3 (10) – 5
30 – 5 = 25
2) 6𝑌 2 Y=2
6 (2) 2 = = 6
3) 2X + 3Y + 4Z, X=4, Y=3, Z=2
2 (4) + 3 (3) +4 (2)
= 25