Assignment - 06-Subtracting Integers
When subtracting integers, we really want to think of the subtraction sign meaning the word opposite. 7 is a positive number, so -7 is just the opposite of that, a negative number. If I were to have -(-8), then I want the opposite of a negative number which is positive, so -(-8) = 8
It is easy to draw a picture when you are subtracting integers that are the same sign. For example: 5-3=2, or -7 – -4 = -3. The pictures would look like below.
The problem comes when we start subtracting numbers of the opposite sign. At that point in time, it is just best to introduce the rule for subtracting. Trust me, if you understand addition of integers, you will appreciate how easy this rule is. When subtracting integers, you simply add the opposite of the second number. Here are some examples:
-6 – 5 : The 5 is positive, so we would rewrite our problem -6 + -5
7 – 9 : Again, the 9 is positive: so we’d rewrite it 7 + -9
8 – -6 : The 6 is negative, so we would rewrite it 8 + 6.
-2 – -3 : The 3 is negative, so we’d rewrite it -2 + 3.
From there, you follow the rules of addition:
1.) Signs same: Add the numbers and keep the sign
2.) Signs different: Find the difference, keep the sign of the larger number
Answering those problems:
Same Sign: -6 – 5 = -6 + -5 = -11
Different Sign: 7 – 9 = 7 + -9 = -2
Same Sign: 8 – -6 = 8 + 6 = 14
Different Sign: -2 – -3 = -2 + 3 = 1