2.1 Introduction to Variables Chapter 2 Understanding Variables and Solving Equations

2.1 Introduction to Variables Objectives Identify variables, constants, and expressions. Evaluate variable expressions for given replacement values. Write properties of operations using variables. Use exponents with variables. Copyright © 2010 Pearson Education, Inc. All rights reserved.

Objective 1: Identify variables, constants, and expressions. A variable a letter that represents a quantity that varies. A constant is a quantity that does not change. Called an expression. Copyright © 2010 Pearson Education, Inc. All rights reserved.

Objective 2: Evaluate variable expressions for given replacement values. Suppose the expression c – 10 represents the number of books a bookstore will order based on the class limit c. Evaluate the expression when the class limit is 32. Example Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 2.1 - 5

Objective 2: Evaluate variable expressions for given replacement values. The number part in a multiplication expression is called the coefficient. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 2.1 - 6

Objective 2: Evaluate variable expressions for given replacement values. The expression can be used to approximate systolic blood pressure of a person that is years old. Evaluate the expression for a person that is 24. Example Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 2.1 - 7

Objective 2: Evaluate variable expressions for given replacement values. Example (continued) Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 2.1 - 8

Objective 2: Evaluate variable expressions for given replacement values. Consider the expression below for finding your average bowling score. Find your average score if you bowl three games and your total score is 378. Example Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 2.1 - 9

Objective 2: Evaluate variable expressions for given replacement values. Example (continued) Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 2.1 - 10

Objective 3: Write properties of operations using variables. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 2.1 - 11

Objective 3: Write properties of operations using variables. Use the variable b to state this property: When any number is divided by 1, the result is the number. Example Use the letter b to represent any number. Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 2.1 - 12

Objective 4: Use exponents with variables. Recall: Now, using variables: Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 2.1 - 13

Objective 4: Use exponents with variables. Rewrite each expression without exponents. (a) y6 (b) 12bc3 (c) –2m2n4 Example Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 2.1 - 14

Objective 4: Use exponents with variables. Evaluate x2 when x is –3. Example Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 2.1 - 15

Objective 4: Use exponents with variables. Evaluate x3y when x is –4 and y is –10. Example Copyright © 2010 Pearson Education, Inc. All rights reserved. Sec 2.1 - 16