The opposite of a whole number is the negative of that number, and the list of negative numbers and whole numbers make up our integers.
… -4, -3, -2, -1, 0 1, 2, 3, 4 …
Note: The number 0 is a little special; it is also considered an integer, but 0 is the opposite of itself.
Why do we need to understand negative numbers?
Negative Numbers are All Around Us
In everyday life, we use the concept of negative numbers all the time. We deal with negative numbers when it comes to money, for instance—more specifically, when you “owe” something.
If you start the day with no money in your pocket (0 dollars) and you borrow three dollars for lunch, you own 3 dollars. That means your lunch money value for the day is (-3).
The next day, you must bring six dollars to school if you want to eat lunch. You need three dollars to pay for yesterday’s lunch (and get your lunch money value back to zero), and three more dollars to buy today’s lunch.
See this worked out in math terms:
0 – 3 = (-3)
(-3) + 6 = 3
Now that you realize that you have been using negative integers for your entire life, you can make sense of this math concept involving negative and positive numbers:
n + (-n) = 0
