2.7 Division of Real Numbers 1 GOAL DIVIDING REAL NUMBERS VOCABULARY reciprocal Since we use reciprocals when dividing, you must be able to write the reciprocal of a number. Remember: The reciprocal of the reciprocal of Since 0 does not have a reciprocal, we cannot divide by 0.

DIVISION RULE To divide a number a by a nonzero number b, multiply a by the reciprocal of b. EXAMPLE 1

Extra Example 1 Find each quotient. a. b. c. d.

2.7 Division of Real Numbers 2 GOAL WORKING WITH ALGEBRAIC EXPRESSIONS Since we divide by multiplying by the reciprocal, the same rules about signs apply. Rules for dividing two real numbers: If the signs are the same, the product is _______. If the signs are different, the product is ________. positive negative EXAMPLE 2

Extra Example 2 Simplify the expression: Multiply by the reciprocal. Use the distributive property. Simplify. EXAMPLE 3

Extra Example 3 Evaluate the expression when x = –5 and y = –1. a. b. c. Undefined

Checkpoint 1. Simplify the expression –5d + 25 2. Evaluate the expression when s = –3 and t = –1. EXAMPLE 4

Extra Example 4 A mountain climber descends 300 feet in 50 minutes. What is her velocity? –300 feet = Velocity Displacement Time VERBAL MODEL LABELS ALGEBRAIC MODEL SOLVE v 50 min EXAMPLE 5

Since 4x cannot equal 0, the domain is all real numbers except x = 0. Extra Example 5 Find the domain of the function Since 4x cannot equal 0, the domain is all real numbers except x = 0.

Checkpoint 1. An elevator descends 120 feet in 1.5 minutes. What is its velocity? 2. Find the domain of the function All real numbers except x = –4.

QUESTIONS?