The document discusses the rule for subtracting integers. The rule states that to subtract, you add the opposite. So for example, 5 - (-3) means 5 + 3, since the opposite of -3 is 3. It provides examples of subtracting integers like -5 - (-3) and -8 - (-4) using the rule. It also has practice problems for students to evaluate expressions with variables like finding a - b - (-6) when a = 8 and b = -15.

1. Subtraction of Integers
I can subtract positive and
negative numbers.

2. Focus Question
 What is the rule for subtracting positive
and negative numbers?

3. The subtraction rule
 Rule: To subtract ADD the OPPOSITE.
 Or – Subtracting is the same as
ADDING THE OPPOSITE.
 5 + (-7) =
 5 – 7 =
-2
-2

4. Example: -5 - (-3)
 ADD the OPPOSITE –5 + (3) = -2
 Notice the subtraction operation
changed to addition, and
 the opposite of –3 becomes 3.
 NOTE: only the number behind
the subtraction sign gets
changed.

5. - 3 – 2
- ADD the OPPOSITE

6. - 3 – 2
- ADD the OPPOSITE
–3 + (-2) = ____-5

7. Two Negatives
 5 - (-3)

8. Two Negatives
 5 - (-3)
 ADD the OPPOSITE 5 + (+3)
 Notice the use of the rule.
 5 - (-3) = 5 + 3 = 8

9. -8 –(-4) + 2
 ADD the OPPOSITE

10. -8 –(-4) + 2
 ADD the OPPOSITE
 –8 + (+4) + 2.

 -8 - (-4) +2
 - 8 + 4 + 2 = - 2

11. Try some with the rule
 -8 – (-10)=
 4 - 7 =
 -9 - 5 =
 -20 – (-4) =
 40 – 32 =

12. Try some with the rule
 -8 – (-10)=
 4 - 7 =
 -9 - 5 =
 -20 – (-4) =
 40 – 32 =
-8 + 10 =
4 + (-7)=
-9 + (-5)=
-20 + 4=
40 + (-32)=
2
-3
-14
-16
8

13. Example:
-7 – 9 - (-4) – 3 + 9 - (-4)=

14. Example:
-7 – 9 - (-4) – 3 + 9 - (-4)=
 Changes on paper to
 –7 + -9 + 4 + - 3 + 9 + 4 =
 Then think DOWN 7, Down 9 more,
then UP 4, Down 3, UP 9, and UP 4.
 The result is –2.

15. EXAMPLE 2 Evaluating a Variable Expression
Evaluate 15 – a – b when a = 24 and b = – 36 .

16. EXAMPLE 2 Evaluating a Variable Expression
Evaluate 15 – a – b when a = 24 and b = – 36 .
15 – 24 – (–36)
=
15 + (–24) + 36 =
–9 + 36 =
27
Add the opposite of 24 and
of –36.
Add –9 and 36.
Substitute 24 for a and –36 for b.
Add 15 and –24.
15 – a – b =

17. GUIDED PRACTICE for Examples 1, 2, and 3
a – b – (–6) a = 8, b = –15

18. GUIDED PRACTICE for Examples 1, 2, and 3
8 – (–15) – (-6)
8 + 15 + 6
29
Add the opposite of –15 and
of –6.
Substitute 8 for a and –15 for b.
Add.
a – b – (–6) a = 8, b = –15

19.  In the Sahara Desert one day it was
136°F.
 In the Gobi Desert a temperature of
-50 F was recorded.
 What is the difference between
these two temperatures?
 Write a subtraction expression to
represent this situation.

20.  Assignment:
No Calculators - show your work