1. Warm-Up 10.1.15 Complete each statement with. 1. −9 −2 2.−80 −81 Find the value of each expression. 3.−9 + 10 4.−6 + (−8) 5.−2 + 2 6.−5 + (−15) + (−10) < > 1 – 14 0 –30

2. Using the Chip Model to Subtract Integers (http://mymathuniverse.com/programs/cmp3/cha nnels/10/channel_content_items/109)http://mymathuniverse.com/programs/cmp3/cha nnels/10/channel_content_items/109

3. Good to Know! When subtracting integers, one method is to make the expression into an addition expression by adding the opposite. Example – 8 – 2 = ? Add the Opposite 1.Change the subtraction to addition. 2.Change the sign of the number after the subtraction sign.  If this number is positive, make it negative.  If it is negative, make it positive. 3.Add. – 8 + (–2) = –10

4. EXPLORE… An algorithm. Use chip models or adding the opposite for the following: 1.Find the differences in each group. 2.Describe what the examples in each group have in common… Group 1 +12 – (+8) -5 – (-7) -4 – (-2) +2 – (+4) Group 2 +12 – (-8) -5 – (+7) -4 – (+2) +2 – (-4)

5. Subtracting Integers 1.Subtract the integers by adding the opposite. 2.Follow the rules for adding integers to determine the sum.

6. Example 1 Use a number line to find the value of –2 – 3. –2 – 3 is –2 + (–3) Add the opposite and use the number line to find the value. –2 – 3 = –5 –2 + (–3) = –5

7. Example 2 Use integer chips to find the value of –5 – (– 4). Subtract the integers by adding the opposite: –5 + 4 –5 – (– 4) = –1 –5 4 + = –1

8. Example 3 The melting point of mercury is approximately –39º C. The melting point of chlorine is approximately –101º C. How much higher is mercury’s melting point than chlorine’s melting point? Write the problem.–39 – (–101) Add the opposite.–39 + 101 Find the sign of the larger101 – 39 = 62 absolute value and subtract. Mercury’s melting point is 62º C higher than chlorine’s melting point.

9. Exit Problems Find the value of each expression. 1.20 − (−8) 2.−11 + 7 3.−6 − 2 4.100 + (−45) 5.30 − 39 6.22 − (−2) 28 –4 –8 55 –9 24