is y a function of x and why


Is it

y = x * 2

or

y = x2

Please tell us, according to your textbook/class-notes:

What is the definition of function?

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The way you answer "is **** a &&&&& " is to look up the definition of "&&&&&" and see if "****" satisfies that definition!

So, what is the definition of "function"?
 
Concept of a Function

Here is another way to understand the concept of a function as I can best define it. We know that y is a function of x when every x value has one unique y value. For example, if these points were in a function: (0,0) (1,0) (2,6), this would be a function because every x value has a unique y value.

However, if you had these points in a function: (0,0) (2,5) (2,10) (3,2), this would not be a function because the x value of 2 has two different y values, 5 and 10.

To determine if a graph is a function, it has to pass the "vertical line test". This is done by simple moving an imaginary line parallel to the y-axis across the entire graph. As long as this line only touches the graph at 1 point at all times, then the function is legitimate.
 
But we are still waiting for sunnysanddevil to get back to us with the definition of "function" he is to use.
 
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