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Pre-Algebra
2-2 Subtracting Integers
2-2 Subtracting Integers
Pre-Algebra
Warm Up
Problem of the Day
Lesson Presentation
Pre-Algebra
2-2 Subtracting Integers
Warm UpAdd.
1. –7 + 2 4. –6 + (–28)
2. –12 + (–9) 5. 104 + (–87)
3. 32 + (–19) 6. –18 + (–24)
Pre-Algebra
2-2 Subtracting Integers
–5 –34
17
–42
–21
13
Pre-Algebra
2-2 Subtracting Integers
Problem of the Day
Copy and complete the magic square. The magic sum is 0.
–8 +3
–2 0
–3
+5
+2
–5+8
Pre-Algebra
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 INTEGERSWords Numbers Algebra
Change the subtraction sign to an addition
sign and change the sign of the
second number.
2 – 3 = 2 + (–3)4 – (–5) = 4 + 5
a – b = a + (–b)a – (–b) = a + b
Pre-Algebra
2-2 Subtracting Integers
Additional Example 1: Subtracting Integers
A. –7 – 4
–7 – 4 = –7 + (–4)
B. 8 – (–5)
8 – (–5) = 8 + 5
C. –6 – (–3)
–6 – (–3) = –6 + 3
= –11
= 13
= –3
Add the opposite of 4.
Add the opposite of –5.
Add the opposite of –3.
Same sign; use the sign of the integers.
Same sign; use the sign of the integers.
6 > 3; use the sign of 6.
Subtract.
Pre-Algebra
2-2 Subtracting Integers
Try This: Example 1
A. 3 – (–6)
3 – (–6) = 3 + 6
B. –4 – 1
–4 – 1 = –4 + (–1)
C. –7 – (–8)
–7 – (–8) = –7 + 8
= 9
= –5
= 1
Add the opposite of –6.
Add the opposite of 1.
Add the opposite of –8.
Same signs; use the sign of the integers.
Same sign; use the sign of the integers.
8 > 7; use the sign of 8.
Subtract.
Pre-Algebra
2-2 Subtracting Integers
A. 8 – j for j = –6
8 – j
8 – (–6) Substitute –6 for j.
Evaluate the expression for the given value of the variable.
= 8 + 6
= 14
Add the opposite of –6.
Same sign; use the sign of the integers.
Additional Example 2A: Evaluating Expressions with Integers
Pre-Algebra
2-2 Subtracting Integers
B. –9 – y for y = –4
= –9 + 4
= –5
Evaluate the expression for the given value of the variable.
–9 – y
–9 – (–4) Substitute –4 for y.
Add the opposite of –4.
9 > 4; use the sign of 9.
Additional Example 2B: Evaluating Expressions with Integers
Pre-Algebra
2-2 Subtracting Integers
C. n – 6 for n = –2
n – 6
–2 – 6 Substitute –2 for n.
Evaluate each expression for the given value of the variable.
= –2 + (–6)
= –8
Add the opposite of 6.
Same sign; use the sign of the integers.
Additional Example 2C: Evaluating Expressions with Integers
Pre-Algebra
2-2 Subtracting Integers
A. 11 – m for m = –3
11 – m
11 – (–3) Substitute –3 for m.
Evaluate the expression for the given value of the variable.
= 11 + 3
= 14
Add the opposite of –3.
Same sign; use the sign of the integers.
Try This: Example 2A
Pre-Algebra
2-2 Subtracting Integers
B. –5 – r for r = –2
= –5 + 2
= –3
Evaluate the expression for the given value of the variable.
–5 – r
–5 – (–2) Substitute –2 for r.
Add the opposite of –2.
5 > 2; use the sign of 5.
Try This: Example 2B
Pre-Algebra
2-2 Subtracting Integers
C. a – 7 for a = –9
a – 7
–9 – 7 Substitute –9 for a.
Evaluate each expression for the given value of the variable.
= –9 + (–7)
= –16
Add the opposite of 7.
Same sign; use the sign of the integers.
Try This: Example 2C
Pre-Algebra
2-2 Subtracting Integers
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?
Additional Example 3: Architecture Application
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
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?
Try This: Example 3
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 3 4
Perform the given operations.
2. –6 – (–4)
3. –9 – 4 + (–3)
2 – 3 – 2 = –3
–2
–16
Pre-Algebra
2-2 Subtracting Integers
Lesson Quiz: Part 2
Evaluate each expression for the given value of the variable.
4. 9 – s for s = –5
5. –4 – w + 5 for w = 21
14
–20
