###### Alissa Fong

MA, Stanford University
Teaching in the San Francisco Bay Area

Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts

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# Relations and Determining Whether a Relation is a Function - Problem 2

Alissa Fong
###### Alissa Fong

MA, Stanford University
Teaching in the San Francisco Bay Area

Alissa is currently a teacher in the San Francisco Bay Area and Brightstorm users love her clear, concise explanations of tough concepts

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The domain is the set of all "x" values and the range is set of all "y" values in a set of ordered pairs. Find the domain by listing all the x values from the relation. Find the range by listing all the y values from the ordered pairs. Repeated values within the domain or range don't have to be listed more than once. In order for a relation to be a function, each x must correspond with only one y value. Use mapping to determine if the relation is a function by listing all the x-values in a column and all the y-values in a column. Draw a line to match the domain value with the corresponding range value. If each x-value has only one y-value associate with it -- for example, in the relation {(3, 1), (4,2), (5, 5)} -- the relation is a function.

In this problem we are asked to find the domain and range and then determine whether or not the relation is a function. Keep in mind the vocabulary domain means the set of all Xs range means the set of all Ys and it would be a function if every x has exactly one y.

So let's check it out. These little bubbly things mean that I have what's called the mapping between my Xs and my Ys so let's see. 3 is matched to 8, 2 is matched to 4, 1 is matched to 8 and 0 is matched to 1. That's what these little arrows mean.

So when I'm asked to find the domain the domain is the set of all Xs, so I'm going to write it like this using this little curly brackets set. So I'll have 3, 2, 1, 0. When you have them out I think it's kind of easy because your domain are like in this bubble and your range is in this bubble, 8, 4, and 1. There we go I found the domain in range.

The next thing it asked me to do is determine whether the relation is a function. It is a function if every x has exactly one y, so let's look. That x has a y that x has a y that okay. Every x has a y no x as like double Ys so we are all done, yes this is the function.

The important thing to remember when you guys are doing problems like this is just vocabulary. Keep your notes handy, keep your self aware of what domain and range are. Domain is the x as range is the y. That's something that is going to be really important for your future Math studies.