Bellwork Oct. 1, 2010Add.

1. –2 + 6 2. –3 + (–4)

3. 7 + (–5) 4. 3 + (–4)

5. –6 + (–1) 6. –6 + 1

4 –7

2 –1

–7 –5

SAME SIGN=SUM

DIFFERENT SIGNS=DIFFERENCE

2-3 Subtracting

Integers

Pg. 88

Essential Question How do you subtract a negative

integer?

A submarine is 58 feet below sea level. An airplane is 264 above sea level. How far above the submarine is the airplane?

The daytime high temperature on the Moon can reach 130 degrees Celsius. At night, the temperature can drop to -110 degrees Celsius. What is the difference between the high and low temperatures?

A music recording company made a net profit of $20,000 in 2009 and had a net loss of $12,000 in 2010. How much did the company’s profits change from 2009-2010?

Subtracting Integers Video Clip

Write down 3 facts about subtracting integers. 1. 2. 3.

Practice with the Professor

http://my.hrw.com/math06_07/nsmedia/homework_help/msm2/msm2_ch02_03_homeworkhelp.html

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

SAME CHANGE CHANGE

1. SAME: Leave the first number alone.

2. CHANGE: Change the sign in the middle from a subtraction sign to an addition sign

3. CHANGE: Change the sign of the second number.

Same- Change- Change

-3 – 2 = Same ChangeChange

- 5

-4 - 3 =

-7-7Same Change Change

EXAMPLE:

Find each difference.

Example 1

A. 5 – (–2)

5 + 2

7

B. –3 – 7

–3 + (–7)

–10

C. – 1 – (–8)

–1 + 8

7

Find each difference.

A. 4 – 2

4 + (–2)

2

B. –2 – (–6)

–2 + 6

4

C. –1 – 4

–1 + (–4)

–5

Example 2

Practice

Practice

6 + -10

Think: 10 – 6 = 4

Largest #: 10

Sign: -

Answer: -4

-3 + 8

Think: 8-3 = 5

Largest #: 8

Sign: +

Answer: 5

Integer War Take out the face cards Red is negative Black is positive Divide the stack of cards in half Each person flip over a card at the same time Decide which person will be the first number in the

subtraction problem. Find the difference of the cards. Write down each problem and answer on your paper. Whoever answers first gets the cards Keep track of your points