How to Find a Function When Given a Relation

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Finding a function when given a relation is something that you can do with groups of ordered pairs. Find a function when given a relation with help from an experienced mathematics educator in this free video clip.

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Video Transcript

Hi, my name is Marija, and today I'm going to show you how to find a function when given a relation. So you can be given a relation in many different ways. I'm going to give it to you today as a group of ordered pairs. And a lot of times you're going to be asked if this given relation is a function. So you have to know what a function is. A function means that every x value has only one y value. So you want to look at all your x values. The three, the one, the four and the three and ask yourself is each of those assigned to exactly one y value. And what you should be able to see right away is that if any of the x values double, it means the answer is no. See this three is assigned to an eight but then it's also later assigned to a five. So the x value three is assigned to two different y values. Which means that this relation right here is not a function. You can also be given a relation as a table of values x and y. So they might be listed like this. Negative one, negative two, three, five and then you might be given y values. And you're asked is this a function. Well the rule is every x has to have only one y. So the fact that all my y's are sixes might be throwing you off, but this in fact is a function. Why. Well if we check every x value, does it correspond to only one y? Negative one corresponds to six. Does it correspond to any other y value? No, just six. Negative two only corresponds to six. Three only corresponds to six and five only corresponds to six. The x's never double up. Therefore, this one is a function.


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