Let's look at a number... 5... Because this is my favorite number!
What number can we add to 5 to get 0 (which is the additive identity) as the answer?
You should be thinking about a negative number. In fact, you should be thinking about a number that is the opposite of 5! -5!
So, the additive inverse of 5 is -5!
Let's go the other way...
What number can we add to -5 to get 0 as the answer?
What's the opposite of -5? 5!
So, the additive inverse of -5 is 5!
Here's the official property:
The Additive Inverse Property:
This is often written in one line...
Where a is any real number and -a is the opposite of a.