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

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: 3+2 4(5) 27-18 3 4 Variable Expressions Examples 𝑋 7 X+2 P-R 4N

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

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)

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)

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) 42 - 4 Multiply 38 Subtract

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) = 14 2 (Divide fraction) =7 Example 3: Evaluate each expression if K = 2, m=7, and X = 4. =3X + 7 (Replace x with 4 ) =3(4) +7 (Multiply 3 and 4) =12 +7 (Add) =19

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)

Let’s check our answers! Evaluate: 3a – 5, A=10 3 (10) – 5 30 – 5 = 25 2) 6𝑌 2 Y=2 6 (2) 2 = 12 2 = 6 3) 2X + 3Y + 4Z, X=4, Y=3, Z=2 2 (4) + 3 (3) +4 (2) 8 + 9 + 8 = 25