Is $K - K = 0$ where $K \in \mathbb{^*R}$ and is positive and infinite?

Question

In the book it is given that $K + (- K)$ is a infinitesimal but it is not explicitly written that $K + (- K)$ is zero. It also states that zero is the only real infinitesimal.

So my question is can I say that $K + (-K)$ is zero for $K \in \mathbb{^*R}$ ? If not why ?

Answer 1

It is true that $a+(-a)=0$ holds for all $a\in\Bbb R$. Now apply the transfer priciple.