Ch 1 Sec 4: Slide #1

Columbus State Community College

Chapter 1 Section 4

Subtracting Integers

Ch 1 Sec 4: Slide #2

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 #3

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

(b) –14

(c) 0

The opposite of 9 is –9 and 9 + –9 = 0

The opposite of –14 is 14 and –14 + 14 = 0

The opposite of 0 is 0 and 0 + 0 = 0

Ch 1 Sec 4: Slide #4

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 #5

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 #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.

(a) 9 – 15

–

Change subtraction to addition.

+9 15–

Change 15 to –15

= –6

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.

(b) –17 – –8

Change subtraction to addition.

+–17 –8–

Change –8 to +8

= –9+

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.

(c) 4 – –12Change subtraction to addition.

4 – –12

Change –12 to 12.

4 + –12

4 + +12

16

Ch 1 Sec 4: Slide #9

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 – 6Change subtraction to addition.

–3 – 6

Change 6 to –6.

–3 + 6

–3 + –6

–9

Ch 1 Sec 4: Slide #10

Change subtraction to addition.Change –10 to 10.

Change 2 to –2.

–5 + +10 + –7 + –2–5 + –10 + –7 + 2

Combining Addition and Subtraction

EXAMPLE 3 Combining Addition and Subtraction

Simplify by completing all the operations.

–5 – –10 + –7 – 2 –5 – –10 + –7 – 2

5 + –7 + –2

–2 + –2

–4

Ch 1 Sec 4: Slide #11

Calculator Tip – TI-30X IIS

(–)

(–)

Example 3: –5 – –10 + –7 – 2

Calculator Tip You can use the negative sign keyon your TI-30X IIS calculator to enter negative numbers.

(–) – +5 10 7 – 2 =(–) (–)

–4

Ch 1 Sec 4: Slide #13

Subtracting Integers

Chapter 1 Section 4 – End

Written by John T. Wallace