1. Variables and Algebraic Expressions 1-3

2. Vocabulary Variable- a letter represents a number that can vary. Constant- a number that does not change. Algebraic expression- consists of one or more variables. It usually contains constants and operations. Evaluate- means to substitute a number for the variable.

3. Evaluate k + 9 for each value of k. Additional Example 1: Evaluating Algebraic Expressions A. k = 5 k + 9 5 + 9 14 Substitute 5 for k. Add. B. k = 2 k + 9 Substitute 2 for k. Add.

4. Check It Out: Example 1 Evaluate a + 6 for each value of a. Solve on your own. A. a = 3 B. a = 5

5. Multiplication and division of variables can be written in several ways, as shown in the table. When evaluating expressions, use the order of operations.

6. Evaluate the expression for the given value of the variable. Additional Example 2: Evaluating Algebraic Expressions Involving Order of Operations A. 4x – 3 for x = 2 4(2) – 3 8 – 3 5 Substitute 2 for x. Multiply. Subtract.

7. Additional Example 2: Evaluating Algebraic Expressions Involving Order of Operations (Solve using the directions given.) B. s ÷ 5 + s, for s = 15 C. 5x 2 + 3x, for x = 2 Substitute 15 for s. Divide. Add. Substitute 2 for x. Evaluate the power. Multiply. Add.

8. Check It Out: Example 2A (Solve on your own) Evaluate the expression for the given value of the variable. A. 3x – 2 for x = 3

9. Evaluate Additional Example 3: Evaluating Algebraic Expressions with Two Variables 6a6a + 4b, for a = 3 and b = 2. 6a6a + 4b 6363 + 4(2) 2 + 8 10 Substitute 3 for a and 2 for b. Divide and multiply from left to right. Add.

10. Check It Out: Example 3 (Solve on your own.) Evaluate 8w8w + 2x, for w = 4 and x = 2.