(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Prove there is a unique element y such that for all x, x+y=x

2. Relevant equations

I also have to prove their is a unique element y such that for all x, xy=x

3. The attempt at a solution

x+y=x, x+y-x=x-x, y=0. xy=x, xy(1/x)=x(1/x). y=1. The problem with the way I did it is that I had to assume the additive and multiplicative inverses are not defined yet. So I have to prove these statements another way. I am not really sure how to though.

I was given a hint which states that for all x, x+y prime=x. Then consider y+y prime and prove that y=y prime. It didnt really help but when I worked through it I found myself using the additive and multiplicative inverses again which I cant use. How does one go about proving these.

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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# Prove their is a unique element y such that for all x, x+y=x

**Physics Forums | Science Articles, Homework Help, Discussion**