1.1 Variables and Equations Objective: To Simplify numerical expressions and evaluate algebraic expressions.

Variable Symbol used to represent one or more numbers Example: x, y, z, a, b, c – The numbers themselves are called the values of the variables – A variable expression is an expression that contains a variable Example: 2x + 4 – An expression that contains only numbers is called a numerical expression Example: 3 + 5

Notation 5 × y can be written as 5y or 5  y or 5(y) To show that a numerical expression has been simplified, please use an = Example = 11

Substitution An expression may be replaced by another expression that has the same value

Example 1 (42÷6)+8 (42÷6)+8 = (42÷6)+8 = = 15 Or (42÷6)

Example 2 Evaluate the expression if a = 4 a.) 7a b.) (3a) + 2 7(4) (3  4)

Example 3 Evaluate (5x) – (3 + y) if x = 12 and y = 9 (5x) – (3 + y) (5  12)-(3+9)

Class Practice Oral Ex. P

Homework Written Ex Page odd