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Proof

(related to Proposition: Algebraic Structure of Real Numbers Together with Addition)

The set of real numbers \(\mathbb R\), together with the specific addition operation "\(+\)" is a commutative group, because:

1. The addition operation is associative, i.e. \((x+y)+z=x+(y+z)\) is valid for all \(x,y,z\in\mathbb R\).
2. We have shown the existence of a neutral element of addition - the number \(0\in\mathbb R\), i.e. such that \(0+x=x\) for all \(x\in\mathbb R\).
3. For every \(x\in\mathbb R\), there there exists an inverse real number \(-x\in\mathbb R\), such that \(x+(-x)=0\).
4. For every \(x\in\mathbb R\), there there exists an inverse real number \(-x\in\mathbb R\), such that \(x+(-x)=0\).
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References

Bibliography

1. Forster Otto: "Analysis 1, Differential- und Integralrechnung einer Veränderlichen", Vieweg Studium, 1983
2. Kramer Jürg, von Pippich, Anna-Maria: "Von den natürlichen Zahlen zu den Quaternionen", Springer-Spektrum, 2013