If a relation contains the points (1,2) and (3,4), what is the domain?

If a relation contains the points (1,2) and (3,4), what is the domain?

• A. {1,2}
• B. {1,3}
• C. {2,4}
• D. {3,4}

Answer: (B)

The domain is the set of all x-values that appear in the ordered pairs. From (1,2) and (3,4), the x-values are 1 and 3, so the domain is {1, 3}. The other options mix in y-values (like 2 and 4) or combine x- and y-values, so they don’t represent all the x-values shown.

The domain is the set of all x-values that appear in the ordered pairs. From (1,2) and (3,4), the x-values are 1 and 3, so the domain is {1, 3}. The other options mix in y-values (like 2 and 4) or combine x- and y-values, so they don’t represent all the x-values shown.