This document defines key concepts related to variables, expressions, and properties in algebra. It explains that a variable is a symbol that represents a number, and numerical and algebraic expressions contain numbers, variables, and operations. It also describes how to evaluate expressions by following the order of operations, which is to evaluate expressions in parentheses first, then exponents, then multiplication and division from left to right, and finally addition and subtraction from left to right.

1. Section 1.2 Variables, Expressions, and Properties

2. Variable A Variable is a symbol, usually a letter, used to represent a number 4 x n a + 7b 5 + r3x – 4 * t t – 2y – 3 + r

3. Numerical Expression Numerical Expression contains numbers and at least one operation. Examples: 3 + 2 17 * 3 20 / 4 14 – 8 21 - 5 + 2 1000 / 8 + 123

4. Algebraic Expression An Algebraic Expression contains variables, numbersand at least one operation symbol. Which of the following is NOT an Algebraic Expression? 4 x n a + 7b 5 + r3x – 4 * t t – 2y – 3 + r

5. Evaluate an Expression To Evaluate an expression means to ‘solve’ the expression. For example: Evaluate the following numerical expressions: 1. 3 + 4 2. 12 / 2 3. 7*6

6. Evaluate the following algebraic expressions, if a=2 b=5 c=8: a + 13 2. 19 – b 3. a * c 1. 2 + 13 2. 19 – 5 3. 2 * 8

7. If an expression has more than one operation you must use: ORDER OF OPERATION

8. ORDER OF OPERATION 1. Evaluate expressions inside grouping symbols. (Parentheses) 2. Evaluate all powers. (Exponents) 3. Do all multiplications and/or divisions from left to right. (Multiplication and Division) 4. Do all additions and/or subtractions from left to right. (Addition and Subtraction) Please Excuse My Dear Aunt Sally