Transcript Document

2-2
2-2 Subtracting
SubtractingIntegers
Integers
Warm Up
Problem of the Day
Lesson Presentation
Pre-Algebra
Pre-Algebra
2-2 Subtracting Integers
Warm Up
Add.
1. –7 + 2
–5
4. –6 + (–28)
2. –12 + (–9) –21 5. 104 + (–87)
3. 32 + (–19)
Pre-Algebra
13 6. –18 + (–24)
–34
17
–42
2-2 Subtracting Integers
Problem of the Day
Copy and complete the magic square.
The magic sum is 0.
Pre-Algebra
+5
–8
+3
–2
0
+2
–3
+8
–5
2-2 Subtracting Integers
Learn to subtract integers.
Pre-Algebra
2-2 Subtracting Integers
Subtracting a smaller number from a
larger number is the same as finding how
far apart the two numbers are on a
number line. Subtracting an integer is the
same as adding its opposite.
SUBTRACTING INTEGERS
Words
Change the
subtraction sign
to an addition
sign and change
the sign of the
second number.
Pre-Algebra
Numbers
Algebra
2 – 3 = 2 + (–3)
4 – (–5) = 4 + 5
a – b = a + (–b)
a – (–b) = a + b
2-2 Subtracting Integers
Additional Example 1: Subtracting Integers
Subtract.
A. –7 – 4
–7 – 4 = –7 + (–4) Add the opposite of 4.
= –11
Same sign; use the sign
of the integers.
B. 8 – (–5)
8 – (–5) = 8 + 5
Add the opposite of –5.
= 13
Same sign; use the sign of
the integers.
C. –6 – (–3)
–6 – (–3) = –6 + 3 Add the opposite of –3.
= –3
6 > 3; use the sign of 6.
Pre-Algebra
2-2 Subtracting Integers
Try This: Example 1
Subtract.
A. 3 – (–6)
3 – (–6) = 3 + 6
=9
Add the opposite of –6.
Same signs; use the sign
of the integers.
B. –4 – 1
–4 – 1 = –4 + (–1) Add the opposite of 1.
= –5
Same sign; use the sign of
the integers.
C. –7 – (–8)
–7 – (–8) = –7 + 8 Add the opposite of –8.
=1
8 > 7; use the sign of 8.
Pre-Algebra
2-2 Subtracting Integers
Additional Example 2A: Evaluating Expressions with
Integers
Evaluate the expression for the given value of
the variable.
A. 8 – j for j = –6
8–j
8 – (–6)
Substitute –6 for j.
=8+6
Add the opposite of –6.
= 14
Same sign; use the
sign of the integers.
Pre-Algebra
2-2 Subtracting Integers
Additional Example 2B: Evaluating Expressions with
Integers
Evaluate the expression for the given value of
the variable.
B. –9 – y for y = –4
–9 – y
–9 – (–4)
Substitute –4 for y.
= –9 + 4
Add the opposite of –4.
= –5
9 > 4; use the sign of 9.
Pre-Algebra
2-2 Subtracting Integers
Additional Example 2C: Evaluating Expressions with
Integers
Evaluate each expression for the given value
of the variable.
C. n – 6 for n = –2
n–6
–2 – 6
= –2 + (–6)
= –8
Pre-Algebra
Substitute –2 for n.
Add the opposite of 6.
Same sign; use the
sign of the integers.
2-2 Subtracting Integers
Try This: Example 2A
Evaluate the expression for the given value of
the variable.
A. 11 – m for m = –3
11 – m
11 – (–3)
Substitute –3 for m.
= 11 + 3
Add the opposite of –3.
= 14
Same sign; use the
sign of the integers.
Pre-Algebra
2-2 Subtracting Integers
Try This: Example 2B
Evaluate the expression for the given value of
the variable.
B. –5 – r for r = –2
–5 – r
–5 – (–2)
Substitute –2 for r.
= –5 + 2
Add the opposite of –2.
= –3
5 > 2; use the sign of 5.
Pre-Algebra
2-2 Subtracting Integers
Try This: Example 2C
Evaluate each expression for the given value
of the variable.
C. a – 7 for a = –9
a–7
–9 – 7
= –9 + (–7)
= –16
Pre-Algebra
Substitute –9 for a.
Add the opposite of 7.
Same sign; use the
sign of the integers.
2-2 Subtracting Integers
Additional Example 3: Architecture Application
The top of the Sears Tower in Chicago, is
1454 feet above street level, while the
lowest level is 43 feet below street level.
How far is it from the lowest level to the top?
1454 – (–43)
Subtract the lowest
level from the height.
1454 + 43
Add the opposite
of (–43).
= 1497
Same sign; use the
sign of the integers.
It is 1497 feet from the lowest level to the top.
Pre-Algebra
2-2 Subtracting Integers
Try This: Example 3
The distance from the high dive to the
swimming pool is 10 feet. The pool is 12 feet
deep. What is the total distance from the high
dive to the bottom of the pool?
10 – (–12)
Subtract the depth of the pool from the
height of the high dive.
10 + 12
Add the opposite of (–12).
= 22
Same sign; use the sign of the integers.
It is 22 feet from the diving board to the bottom
of the pool.
Pre-Algebra
2-2 Subtracting Integers
Lesson Quiz: Part 1
1. Write a subtraction equation for the number
line diagram.
–4 –3 –2 –1
0
1
2
2 – 3 – 2 = –3
Perform the given operations.
2. –6 – (–4)
–2
3. –9 – 4 + (–3) –16
Pre-Algebra
3
4
2-2 Subtracting Integers
Lesson Quiz: Part 2
Evaluate each expression for the given
value of the variable.
4. 9 – s for s = –5
14
5. –4 – w + 5 for w = 21
–20
Pre-Algebra