1. Subtracting Integers Chapter 11-4

2. Using a number line  You can use a number line to model the subtraction of integers.  The subtraction operation tells you to turn around and face the opposite direction.  You start at zero facing the positive direction.  You move forward for a positive integer.  You move backward for a negative integer.

3. Example  Find 4 - (-2) using a number line. Start at zero. Face the positive direction. Move forward 4 units for 4. Turn around. Then move backward 2 units for -2. You stop at 6. -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6

4. You Try! 1.) 4 – (-1) = 5 2.) -2 – (-4) = 2 3.) 1 - 5 = -4 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6

5. Rules  Subtracting an integer is the same as adding its opposite. KCOKCO Keep Change Opposite  Keep first integer  Change subtraction symbol to addition  Take the opposite of the second number.  Use rules for adding integers.

6. Example: -3 – (-6) -3 – (-6) k c o Keep the -3 Change the subtraction to addition + Change -6 to +6. -3 - (-6) = -3 + (+6)= 3

7. You Try!  Use KCO to solve. 1.) -1 – (-1)= 0 2.) 2 – 7 = -5 3.) 12 – (-17) 29 4.) -9 – 8=

8. You Try!  Use the number line or your rules to solve the following: You are at the highest point of Lost Mine Trail. Your elevation is 6,850 feet. You hike down the trail to an elevation of 5,600 feet. What integer represents your current elevation?  6,850 – 5,600 = 1,250  Your current elevation is 1,250 feet.