Math 2.0

Associative rings and algebras Definition

Subring

Builds on Ring

Definition

Let RR be a ring. A subring of RR is a subset S⊆RS \subseteq R with these properties.

  1. 1∈S1 \in S.
  2. If a,b∈Sa, b \in S, then a−b∈Sa - b \in S.
  3. If a,b∈Sa, b \in S, then a⋅b∈Sa \cdot b \in S.

A subring SS is a ring with the addition and the multiplication of RR, restricted to SS.

Remarks

The integers ℤ\mathbb{Z} are a subring of ℚ\mathbb{Q}, and ℚ\mathbb{Q} is a subring of ℝ\mathbb{R}. The set 2ℤ2\mathbb{Z} of even integers is closed under addition and multiplication, but it is not a subring of ℤ\mathbb{Z}, because 1∉2ℤ1 \notin 2\mathbb{Z}. Authors who do not require a ring to have an identity also do not require 1∈S1 \in S.

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  1. Group concept
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126 pages build on this one.

Further reading

  1. Web https://en.wikipedia.org/wiki/Subring, Definition
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