# How to know if y is a function of x

If the answer is yes, then y is a function of x. If the answer is no, then y isn’t a function of x. Example: Let y = 2x -5. Let x = 4. Then, y = 2*4 - 5 = 3. Let x = -3. Then y = 2(-3) - 5 = -6–5 = -11. Notice that for every x, I get exactly one y-value.

## Identify Functions Using Graphs

y is a function of x if for every value of x in the domain of definition, where x takes its values, there corresponds only one value of y. So, y=x-3 represents y as a function of x. Note more

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## Checking if an equation represents a function

You can also tell this is a function because for any value of x you use in this function, there will be exactly one y value corresponding to that value of x. No more than one y

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## How Do You Figure Out If a Relation is a Function?

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