Let's review the 3 methods we can use to add integers with different signs:
1. Use a number line. From your starting point, move to the right if adding a positive integer; move to the left if adding a negative integer.
2. Use the method you have in your notes:
1. Find the absolute values of the two numbers (ignore the negatives).
2. Find the difference between the absolute values.
3. Keep the sign of the number with the greatest absolute value.
Example:
-7 + 4
|-7| + |4|
7 - 4 -----> Notice that after we determined the absolute value, we changed it to subtraction.
= 3 -----> Since the number with the greatest absolute value was -7, the answer becomes negative.
= - 3
3. Use counters/the "Integer Wars" method! Place negative and positive symbols inside a shape of your choosing.
The following picture represents 4 + (-5):
Since 1 positive is cancelled out by one negative, we are left with this, which represents -1:
And voila! You have your answer :) You can also think of it like a battle: There is a negative side and a positive side. Which side has more? The negative side, so we know our answer will be negative. By how many? One more - so we know our answer will be -1.
If you're having a hard time adding integers in your head, any of these 3 methods will help you out. Happy adding!
