Transcript Subtraction of Real Numbers

2.3 Subtraction of Real Numbers
GOAL
1
SUBTRACTING REAL NUMBERS
To subtract a real number, ____
add its ________.
opposite
Example:
Rewrite by adding the opposite:
Add:
EXAMPLE 1
6  ( 4)
64
10
EXAMPLE 2
Extra Example 1
a. –6 – 3
6  ( 3)
9
1 2

b.
2 3
1  2
  
2  3

1
6
c. –15 – (–6)
15  6
9
See page 781 for review on
adding fractions.
Extra Example 2
Simplify the expression: 10 – 5 + 14 – (–18).
10  ( 5)  14  18
5  14  18
19  18
EXAMPLE 3
37
Extra Example 3
Find the terms of 3x – 5.
First, rewrite the expression as addition: 3 x  ( 5)
The terms are 3x and –5.
EXAMPLE 4
Extra Example 4
Evaluate the function y = –x – 7 for these values of x: –2,
–1, 0, and 1. Organize your results in a table and describe
the pattern.
Input
Function
Output
2
y  ( 2)  7
 2  ( 7)
5
1
y  ( 1)  7
 1  ( 7)
6
0
y  (0)  7
 0  ( 7)
7
1
y  (1)  7
 1  ( 7)
8
Pattern:
Each time x increases
by 1, y decreases by 1.
Checkpoint
1. Evaluate the expression: –5 – (–3) + 4 – 1.
2. Find the terms of –7 – (–2x ).
1
–7 and 2x
3. Evaluate the function y = 1 – x for these values of x: –2, –1,
0, and 1. Organize your results in a table and describe the
pattern.
x
y
–2
3
–1
2
0
1
1
0
As x increases by 1, y decreases by 1.
2.3 Subtraction of Real Numbers
GOAL
2
USING SUBTRACTION IN REAL LIFE
In reporting gains or losses, it is common practice to use a
plus sign (+) to indicate a gain and a minus sign (–) to indicate
a loss. Note their use in examples 5 and 6.
EXAMPLE 5
EXAMPLE 6
Extra Example 5 and 6
The daily closing prices of a utilities stock for one week are
given below.
a) Find the change in the closing price from day to day.
b) Write the changes you found in order.
c) Find the difference of the greatest number and the least
number.
b. 4.13,  2.32, 0.75, 1.34
c. 1.34  ( 4.13)  5.47
122.76 – 121.42 = +1.34
123.51 – 122.76 = +0.75
121.19 – 123.51 = –2.32
117.06 – 121.19 = –4.13
Checkpoint
1. The daily closing prices of a software company’s stock
for one week are given below.
a) Find the change in the closing price from day to day
b) Write the changes in order. –5.7, –3.9, –2.1, 1.5
c) Find the difference of the greatest number and the least
number. 7.2
a.
–5.7
+1.5
–2.1
–3.9
QUESTIONS?