1. Adding Integers
Section 2 - 4

2. Vocabulary
Opposites refer to numbers being the same distance away from 0.
Example: – 6 is the opposite of 6
Opposite of… 8?
-13?
-10? 0?

3. What direction do I go? When adding? When subtracting?
When adding a negative?
So, what do you think a negative sign means?
Go in the opposite direction!
Need to Know
A minus sign and a negative sign has the same effect
right
left
left

4. The short explanation!
Keep it simple, work with just 2 numbers at a time
Integers with same sign, add the numbers, and the answer takes the sign.
The rule:
positive + positive = add #’s, then positive
negative + negative = add #’s, then negative
ex: – 5 + – 13 = – 18

5. IF, the integers have opposite signs, follow these steps:
The tricky rule…
IF, the integers have opposite signs, follow these steps:
positive + negative
negative + positive
Step 1: just look at the number without the sign.
Step 2: SUBTRACT (big – small)
Step 3: answer takes sign of the bigger number.

6. Example: – 5 + 13 = – 15 + 9 = Step 1: becomes 13 – 5 = 8
Step 2: since 13 is positive, answer = 8
– =
Step 1: becomes 15 – 9 = 6
Step 2: since 15 is neg., answer = – 6

7. Example: 17 + – 23 = – 18 + 29 = Step 1: becomes 23 – 17 = 6
Step 2: since 23 is neg., answer = – 6
– =
Step 1: becomes 29 – 18 = 11
Step 2: since 29 is pos., answer = 11

8. If it’s too hard… Step 1: Draw a number line
Step 2: Put your finger where the first number is located.
Step 3: Move
Right: if you add a positive number
Left: if you add a negative number
The answer is where you end up.
*Be sure to count carefully.

9. Keeping it simple Work with 2 numbers at a time
When substituting negative integers for variables, put that number in ( ).
Last resort, use a number line.
Always ask yourself,
“Is the answer positive or negative?”

10. Practice – 5 + – 8 = ? – 25 + 13 = ? 5 + – 33 = ? 115 + – 133 = ?
– 17 + (– 18) = ?
– = ?
55 + – 84 = ?
– = ?

11. Practice, with variables
Suppose a = – 8, b = 12, and c = – 4
5 + a = ?
c + (– 5) = ?
b + c = ?
a + c = ?
21 + c = ?

12. Worksheet Skills Practice 2-4 Homework Food for thought:
Test over integers & coordinate planes on Friday, October 3!
Worksheet
Skills Practice 2-4
Food for thought:
If adding a negative goes in the opposite direction of adding, what happens if I subtract a negative?