2-3 subtracting integers problem of the day add. 1. –2 + 62. –3 + (–4) 3. 7 + (–5)4. 3 +...

2-3 Subtracting Integers

Problem of the DayAdd.

1. –2 + 6 2. –3 + (–4)

3. 7 + (–5) 4. 3 + (–4)

5. –6 + (–1) 6. –6 + 1

4 –7

2 –1

–7 –5


Use a number line to find each difference.

Additional Example 1A: Modeling Integer Subtraction

4 – 1

–2–1 0 1 2 3 4 5 6

4

–1

4 – 1 = 3

Start at 0. Move right 4 spaces. To subtract 1,move to the left.


Rules for Subtracting Integers:

Add the opposite1. copy 2. change 3. opposite

4. Follow the Rules of Adding Integers.


Additional Example 1B: Modeling Integer Subtraction

1 2 –6–5–4 –3 –2–1 0


–3 – 1–3–1

–3 – 1 = –4

Start at 0. Move 3 spaces left. To subtract 1,move to the left.


Additional Example 1C: Modeling Integer Subtraction


–2 – (–4)

1 2 3 4 –4 –3 –2–1 0

–2

–(–4)

–2 – (–4) = 2

Start at 0. Move left 2 spaces. To subtract –4,move to the right.


Check It Out: Example 1A


–4 –(–2)

1 2 3 4 –4–3–2–1 0

–(–2)–4

–2


Check It Out: Example 1B


5 – (–1)

6 7 –1 0 1 2 3 4 5

–6

5 –(–1)


Addition and subtraction are inverseoperations—they “undo” each other.Instead of subtracting a number youcan add its opposite.


Find each difference.

Additional Example 2: Subtracting Integers by Adding the Opposite

A. 5 – (–2)

5 + 2

7

B. –3 – 7

–3 + (–7)

–10C. – 1 – (–8)

–1 + 8

7

Add the opposite of –2.

Add the opposite of 7.



Check It Out: Example 2


A. –1 –4

–1 –4 = 1 + (–4)

= -5

B. –6 –3

–6 –3 = –6 + (–3)

= -9C. 5– (– 6)

5 – (– 6) = 5 + 6

=11




D. 7 – (–2)

7 – (–2) = 7 + 2

= 9


Evaluate x – y for each set of values.

Additional Example 3: Evaluating Expressions with Integers

A. x = –3 and y = 2

x – y

–3 – 2 = –3 + (–2)

= –5

B. x = 4 and y = –6

x – y

4 – (–6) = 4 + 6

= 10

Substitute for x and y.

Add the opposite of 2.

Substitute for x and y.

Add the opposite –6.



Evaluate x – y for each set of values.

A. x = –4 and y = –3

x – y = –4 –(–3)

= –4 + 3

= –1

B. x = 24 and y = 20

= 24 + 20

= 44

x – y = 24 –(–20)


Additional Example 4: Temperature Application

Find the difference between 32°F and –10°F.

32 – (–10)

32 + 10 = 42

The difference in temperature is 42˚F.




Find the difference between 8 °F and -5 °F

8 –(–5) = 8 + 5

= 13

The difference is 13 °F.


Standard Lesson Quiz

Lesson Quizzes

Lesson Quiz for Student Response Systems


Lesson Quiz: Part I

Use a number line to find the difference.

1. 3 – 9


2. –7 – 4

3. –3 – (–5)

4. Evaluate x – y + z for x = –4, y = 5, and z = –10.

–11

–6

2

–19


Lesson Quiz: Part II

5. On January 1, 2002, the high temperature was 81˚F in Kona, Hawaii. The low temperature was –29˚F in Barrow, Alaska. What was the difference between the two temperatures?

110˚F


1. Identify the number line that helps to find the difference.

5 – 15

A. –20

B. –10



2. Identify the difference.

–8 – 5

A. 13

B. 3

C. –3

D. –13



3. Identify the difference.

–2 – (–6)

A. –8

B. –4

C. 4

D. 8



4. Evaluate x – y + z for x = –6, y = 4, and z = –12.

A. –22

B. –12

C. –10

D. –2




5. In January 2002, the mean temperature was –26 °F in McMurdo, Antarctica. The mean temperature was 37 °F in London. What was the difference between the two temperatures?

A. –63 °F

B. –52 °F

C. 52 °F

D. 63 °F

2-3 subtracting integers problem of the day add. 1. –2 + 62. –3 + (–4) 3. 7 + (–5)4. 3 +...

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