What is the inverse for numbers under addition?
A number and its additive inverse add up to zero.
If a number has no sign, add a "-" in front of it to get its
additive inverse. The additive inverse of 5 is -5. The additive
inverse of x is -x.
If a number has a minus sign, take it away to get its additive
inverse. The additive inverse of -10 is 10. The additive inverse of
-y is y.