Download 3 Subtracting Integers

Subtracting Integers
Slide #1
Subtracting Integers
1. Find the opposite of a signed number.
2. Subtract integers.
3. Combine adding and subtracting of integers.
Slide #2
Subtracting Integers
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
(c)
0
The opposite of 0 is 0 and
–14
+ 14 = 0
0 + 0 = 0
Slide #3
Subtracting 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.
Slide #4
Subtracting Integers
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.
Slide #5
Subtracting 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
Change 15 to –15
Change subtraction to addition.
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
+–
Change subtraction to
addition.
–+8
=
–9
Change –8 to +8
Slide #7
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
4 + –12
4 + +12
Change subtraction to
addition.
Change –12 to 12.
16
Slide #8
Subtracting 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
–3
–
+
6
6
Change subtraction to
addition.
Change 6 to –6.
–3
+ –6
–9
Slide #9
Subtracting Integers
EXAMPLE 3
Combining Addition and Subtraction
Simplify by completing all the operations.
–5
– –10 + –7 – 2
Change subtraction to addition.
Change –10 to 10.
Change 2 to
–2.
–5
– –10 + –7 – 2
–5
+ +–10 + –7 + –2
5
+ –7 + –2
–2
+ –2
–4
Slide #10
Subtracting Integers
Calculator Tip You can use the negative sign key (–)
on your TI-30X IIS calculator to enter negative numbers.
Example 3: –5 – –10 + –7 –
(–)
5
–
(–)
10
+
(–)
7
2
–
2
=
–4
(–)
Slide #11