Domain and range

ashleejae259

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Oct 5, 2011
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use the relation {(-4,3), (-1,0), (0,-2), (2,1), (4,3)} to answer the following questions.
A. state the domain of the relation
B. state the range of the relation
C. Is the relation a function? how do you know?

please helpp???;)
 
The domain is the set of numbers that appear FIRST in the ordered pairs.

The range is the set of numbers that appear SECOND in the ordered pairs.

If all of the ordered pairs have DIFFERENT second elements, the relation is a function.


Here's an example of a similar problem:

{(1, 3), (2, 4), (-2, -4), (0, 0)}

domain = {1, 2, -2, 0}
range = {3, 4, -4, 0}

Since all of the ordered pairs have DIFFERENT second elements, this is a function.

You have this backward. If all of the first coordinates are different,
then it doesn't matter if the second coordinate is repeated or not.
It will (still) be a function.

Examples:

{(2, 5), (7, 5)} is a function.


{(2, 3), (2, 8)} is not a function.

One way of looking at is if they are plotted as points,
they fail the vertical line test for a function.

The reason you gave why your example is a function is not correct.
The reason your example is a function is that all of your first coordinates
are different from each other.
 
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