a + -a 0. Example1: 3/4 + (-3/4) 0 Example2: 4/5 + (-4/5) 0 Example3: 2 + (-2) 0 Example4: 100 + (-100) 0
The thing fundamentally wrong with your question is that the additive inverse of a number a is DEFINED as the number b such that a + b 0. You can't possibly hope to justify a definition, you can just illustrate it. eg. The additive inverse of 2 is (-2) as 2 + (-2) 0. The additive inverse of 1/2 is (-1/2) as 1/2 + (-1/2) 0. The additive inverse of 2/5 is (-2/5) as 2/5 + (-2/5) 0. The additive inverse of 1 is (-1) as 1 + (-1) 0.
