Prove Ring with Identity on Set S with One Element x

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Discussion Overview

The discussion revolves around proving that a set S with exactly one element x can be considered a ring by verifying the necessary ring axioms. Participants explore the properties of addition and multiplication defined on this set, examining associativity, commutativity, identity, and inverses.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes that to show S is a ring, one must verify axioms such as associativity, commutativity, identity, and inverses for addition, as well as commutativity for multiplication.
  • Another participant points out that since both the additive identity and the additive inverse can be defined as x, there is no issue with having an additive inverse in this context.
  • A participant confirms that multiplication commutativity holds, citing the associativity of multiplication and the distributive property as applicable in this case.
  • There is a suggestion to check the list of ring axioms on Wikipedia for further clarification on the requirements for a set to be classified as a ring.

Areas of Agreement / Disagreement

Participants generally agree on the definitions and properties of addition and multiplication in this context, but there is uncertainty regarding whether all ring axioms have been sufficiently addressed, particularly concerning the completeness of the proof.

Contextual Notes

Some assumptions about the definitions of identity and inverses are implicit, and the discussion does not resolve whether all necessary axioms have been fully verified for S to be classified as a ring.

Stephen88
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On a set S with exactly one element x,
define x + x = x, x*x = x. Prove that S is a ring.
The way I think about this problem is be showing that it verifies certain axioms...like associativity,commutativity,identity,inverse for addition and commutativity for multiplication and a (b + c) = ab + ac .. (a + b) c = ac + bc.
For Addition the first two i think it is obvious since
1.x+x=x+x..
2.(x+x)+x=x+(x+x)
For Identity since x+x=x then 0_S=x.
For the inverse I don't see how since the set has only one element x which equal 0_S...I guess I don't have to check the last two axioms because S is not a ring.
Am I doing this right?
 
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We have x + (-x) = 0 where both -x and 0 are defined to be x, so there is no problem with an additive inverse.
 
uh sorry...yes that is true then for multiplication commutativity (x*x)*=x*(x*x) and also x(x+x)=x +x and (x+x)x=x+x again.Will this suffice or is there something else.?..because it seemed quite short.
 
StefanM said:
for multiplication commutativity (x*x)*=x*(x*x)
The fact (x * x) * x = x * (x * x) is called associativity.

StefanM said:
x(x+x)=x +x and (x+x)x=x+x again.
Distributivity says x(x+x) = x * x + x * x and (x+x) * x = x * x + x * x.

StefanM said:
Will this suffice or is there something else.?..because it seemed quite short.
Why don't you check the list of ring axioms, for example, in Wikipedia?
 

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