TheoremBase

The Integers Form an Ordered Ring Containing the Natural Numbers as Its Positive Elements

The integers form an ordered commutative ring; negation behaves as expected; the embedding of N is injective and preserves 1, sums, products and the order; [a, b] = ι(a) − ι(b); every integer is positive (the image of N), zero or negative; and there are no zero divisors, so nonzero factors cancel and positive factors preserve the strict order.

Statement

In the setting of The Natural Numbers and the Natural Numbers with Zero: Arithmetic, Order, Induction and Recursion, let Z\mathbb{Z}, [a,b][a,b], its operations and order, 0Z0_{\mathbb{Z}}, 1Z1_{\mathbb{Z}} and ι\iota be as in The Integers §integers, The Integers §operations, The Integers §constants and The Integers §embedding. Let x,y,z∈Zx,y,z\in\mathbb{Z} and a,b∈Na,b\in\mathbb{N}.

Z\mathbb{Z}, with ++, ⋅\cdot, 0Z0_{\mathbb{Z}} and 1Z1_{\mathbb{Z}}, is a commutative ring, and x+(−x)=0Zx+(-x)=0_{\mathbb{Z}}.

≤\le is a total order on Z\mathbb{Z}, with << as its strict relation, and Z\mathbb{Z}, with ++, ⋅\cdot, 0Z0_{\mathbb{Z}}, 1Z1_{\mathbb{Z}} and ≤\le, is an ordered ring.

−(−x)=x-(-x)=x, 0Z⋅x=0Z0_{\mathbb{Z}}\cdot x=0_{\mathbb{Z}} and (−x)⋅y=−(x⋅y)(-x)\cdot y=-(x\cdot y).

ι\iota is injective, ι(1)=1Z\iota(1)=1_{\mathbb{Z}}, ι(a+b)=ι(a)+ι(b)\iota(a+b)=\iota(a)+\iota(b), ι(ab)=ι(a) ι(b)\iota(ab)=\iota(a)\,\iota(b), and a<ba<b if and only if ι(a)<ι(b)\iota(a)<\iota(b).

[a,b]=ι(a)−ι(b)[a,b]=\iota(a)-\iota(b).

Exactly one of the following holds: x=ι(n)x=\iota(n) for some n∈Nn\in\mathbb{N}; x=0Zx=0_{\mathbb{Z}}; x=−ι(n)x=-\iota(n) for some n∈Nn\in\mathbb{N}.

0Z<x0_{\mathbb{Z}}<x if and only if x=ι(n)x=\iota(n) for some n∈Nn\in\mathbb{N}.

If xy=0Zxy=0_{\mathbb{Z}}, then x=0Zx=0_{\mathbb{Z}} or y=0Zy=0_{\mathbb{Z}}.

If z≠0Zz\neq0_{\mathbb{Z}} and xz=yzxz=yz, then x=yx=y.

If x<yx<y and 0Z<z0_{\mathbb{Z}}<z, then xz<yzxz<yz.

If 0Z<z0_{\mathbb{Z}}<z, then x≤yx\le y if and only if xz≤yzxz\le yz.

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