3.05] The domain of the following relation: R: {(−4, 3), (3, 6), (−2, 1), (3, 6)} is

{1, 3, 6}

{−4, 3, −2, 3}

{−4, −2, 3}

No domain exists

Question

3.05] The domain of the following relation: R: {(−4, 3), (3, 6), (−2, 1), (3, 6)} is 

 {1, 3, 6} 

 {−4, 3, −2, 3} 

 {−4, −2, 3} 

 No domain exists

anonymous · Answer

The answer is the third choice -- {-4, -2, 3}.
The domain is just the x values of a relationship. Or, in other words, the domain is the first value in each ordered pair. 
The second answer choice has the same set of numbers, but you don't need to repeat the same number when it is used more than once. Also, it's standard to place the numbers in order from least to greatest.