# Thread: Domain of the relation

1. ## Domain of the relation

My problem states:

Determine the domain of the relation, and determine whether the relation describes y as a function of x:

y=|x|

2. ## Re: Domain of the relation

Originally Posted by Kibbygirl
My problem states: Determine the domain of the relation, and determine whether the relation describes y as a function of x: y=|x|
A relation is a set of ordered pairs.
In this case: $\displaystyle \{(x,|x|)\}$.
The domain is the set of first terms. What is this set of values?

If no two pairs can have the same first term then the relation is a function on the domain.
Is this relation a function?

3. ## Re: Domain of the relation

Would the domain just be x then? I'm not understanding what the domain would be when it is just listing a variable - though does the bars mean "absolute"?

4. ## Re: Domain of the relation

Originally Posted by Kibbygirl
Would the domain just be x then? I'm not understanding what the domain would be when it is just listing a variable - though does the bars mean "absolute"?
1. As Plato pointed out the domain is a set. Since there aren't any restrictions we can assume that x has real values. Therefore the domain is the set of all real numbers: $\displaystyle \mathbb{R}$

2. $\displaystyle abs(a) = |a|$