1. 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.

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

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

4. 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

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

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

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

8. 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

9. 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.

10. 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.

11. QUESTIONS?