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Chapter 1 Section 4
Subtracting Integers
Ch 1 Sec 4: Slide #1
Subtracting Integers
1. Find the opposite of a signed number.
2. Subtract integers.
3. Combine adding and subtracting of integers.
Ch 1 Sec 4: Slide #2
Finding the Opposites of Signed Numbers
EXAMPLE 1
Finding the Opposites of Signed Numbers
Find the opposite (additive inverse) of each number. Show that the
sum of the number and its opposite is 0.
(a)
9
The opposite of 9 is –9
and
9 + –9 = 0
(b)
–14
The opposite of –14 is 14
and
–14
(c)
0
The opposite of 0 is 0
and
0 + 0 = 0
+ 14 = 0
Ch 1 Sec 4: Slide #3
Subtracting Two Integers
Subtracting Two Integers
To subtract two numbers, add the first number to the opposite of
the second number. Remember to change two things:
Step 1 Make a pencil stroke to change the subtraction symbol to
an addition symbol.
Step 2 Make a second pencil stroke to change the second number
to its opposite. If the second number is positive, change it
to negative. If the second number is negative, change it to
positive.
Ch 1 Sec 4: Slide #4
CAUTION
CAUTION
When changing a subtraction problem to an addition problem, do
not make any change in the first number. The pattern is
1st number – 2nd number = 1st number + opposite of 2nd number.
Ch 1 Sec 4: Slide #5
Subtracting Two Integers
EXAMPLE 2
Subtracting Two Integers
Make two pencil strokes to change each subtraction problem into
an addition problem. Then find the sum.
(a)
9 – 15
9 +–
– 15
=
–6
Changeto15addition.
to –15
Change subtraction
Ch 1 Sec 4: Slide #6
Subtracting Two Integers
EXAMPLE 2
Subtracting Two Integers
Make two pencil strokes to change each subtraction problem into
an addition problem. Then find the sum.
(b)
–17
– –8
–17
+–
–+8
=
–9
Changeto–8addition.
to +8
Change subtraction
Ch 1 Sec 4: Slide #7
Subtracting Two Integers
EXAMPLE 2
Subtracting Two Integers
Make two pencil strokes to change each subtraction problem into
an addition problem. Then find the sum.
(c)
4 – –12
4 – –12
Change subtraction to addition.
4 + –12
Change –12 to 12.
4 + +12
16
Ch 1 Sec 4: Slide #8
Subtracting Two Integers
EXAMPLE 2
Subtracting Two Integers
Make two pencil strokes to change each subtraction problem into
an addition problem. Then find the sum.
(d)
–3
– 6
–3
– 6
Change subtraction to addition.
–3
+ 6
Change 6 to –6.
–3
+ –6
–9
Ch 1 Sec 4: Slide #9
Combining Addition and Subtraction
EXAMPLE 3
Combining Addition and Subtraction
Simplify by completing all the operations.
–5
– –10 + –7 – 2
–10 to
ChangeChange
subtraction
to10.
addition.
Change 2 to
–2.
–5
– –10 + –7 – 2
–5
+ +–10 + –7 + –2
5
+ –7 + –2
–2
+ –2
–4
Ch 1 Sec 4: Slide #10
Calculator Tip – TI-30X IIS
Calculator Tip
You can use the negative sign key
on your TI-30X IIS calculator to enter negative numbers.
Example 3:
(–)
5
–
(–)
10
–5
(–)
– –10 + –7 – 2
+
(–)
7
–
2
=
–4
(–)
Ch 1 Sec 4: Slide #11
Subtracting Integers
Chapter 1 Section 4 – End
Written by John T. Wallace
Ch 1 Sec 4: Slide #13