Variables are symbols that represent numbers, expressions are mathematical phrases that can contain numbers or variables. Simplifying an expression replaces it with an equivalent expression having as few terms as possible using the substitution principle and order of operations without changing the value. A formula uses variables, expressions, and the order of operations.

1. Lesson 1.1: Variables, Expressions,
and the Order of Operations
• Variable: A symbol used to represent one or more
numbers
• Expression: A mathematical phrase
o Numerical Expression: Contains only numbers
o Algebraic Expression:
Contains one or more variables
• Simplify an Expression: Replace an
expression with an equivalent expression
having as few terms as possible

2. Substitution Principle: Replacing a
numerical expression by its value, or
replacing a variable by its given value does
not change the value of an expression

3. Order of Operations

4. Use a Formula