Definition Question

1. Sep 1, 2011

Miike012

Commutative Ring: Let R be a set of elements a,b,c .... for which the sum (a + b) and the product (ab) of any two elements a and b of R are defined is called a commutative ring

This is my understanding, tell me if I am wrong....

f(x) = 1/x
Domain of f: { x | x =/ 0 } = A

Thus any two integers (a + b) = 0 and (ab) = 0 are not in the commutative ring..... commutative ring being A
Is this correct?

Last edited: Sep 1, 2011
2. Sep 1, 2011

Tomer

Why are you saying that for every two integers a,b in A a+b = 0 holds?

This set is not even a ring (let alone a commutative ring) because it fails to hold a certain axiom. Any guesses which one? Can you prove it?

3. Sep 1, 2011

Miike012

I just opened the book.. Never took a class on this... so I am confused ab out why this definition is important.
And I was hoping for an example for the definition....

It also goes on to say that it must follow 8 rules

4. Sep 1, 2011

Tomer

http://en.wikipedia.org/wiki/Ring_(mathematics [Broken])

Last edited by a moderator: May 5, 2017
5. Sep 1, 2011

HallsofIvy

Staff Emeritus
A "ring" consists of a set of objects together with two operations, * and +, satisfying a lot of requirements- mostly those for the integers with regular addition and subtraction. You have defined your set, A, the set of all nonnegative numbers, but have not defined addition or subtraction. If you intended "regular" addition of numbers, this is not a ring because it does not have an "additive identity"- you have specifically excluded 0 which is the identity for "regular" addition.