Chapter 1: Variables, Function Patterns, and Graphs 1.1 Using Variables

Variables A symbol, usually a letter, that represents an unknown quantity

Expression vs Equation Algebraic expression: a mathematical phrase that can include numbers, variables, and operation symbols – Does not have an equals sign Equation: a statement that two expressions are equal to each other – Has an equals sign

Example 1 Write an algebraic expression for each phrase: Seven more than n The difference of n and 7 The product of seven and n The quotient of n and seven

Example 2 Define a variable and write an algebraic expression for each phrase: Two times a number plus five Seven less than three times a number

Example 2a Define a variable and write an algebraic expression for each phrase: Nine less than a number The sum of twice a number and 31

Equations Mathematical sentence that uses an equal sign If true, then the expressions on either side represent the same value If there’s one or more variables, the equation is an open sentence “is” suggests an equal sign

Example 3 Track One Media sells all CDs for $12 each. Which equation best represents the cost c of a given number n of CDs? 12 + c = n n + 12 = c 12c = n c = 12n

Example 3a Suppose the manager at Track One Media uses the equation c = 10.99n. What could this mean?

Homework P even