Understanding f(x) and y in the function f(x) = x² + 4: Explained

thomas49th · Jan 3, 2008

When you say f(x) = x² + 4 (the function of f is defined at x² + 4)
is that the same as saying y = x² + 4?

slider142 · Jan 3, 2008

Only if you set y=f(x). f(x) is a function assigning the value f(x) to each input x. y = f(x) is just an equation, which can be graphed on a Cartesian plane; it is a method of visualizing the properties of the function.

HallsofIvy · Jan 4, 2008

thomas49th said:

When you say f(x) = x² + 4 (the function of f is defined at x² + 4)
is that the same as saying y = x² + 4?

Did you mean "defined as [itex]x^2+ 4[/itex].

No, that is NOT the same as saying "y= [itex]x^2+ 4[/itex]" unless, as slider142 said, you define y= f(x). If you are graphing such a function on an standard "xy coordinates sytem" then the first thing you should say is "let y= f(x)". That is so standard that it is not always said.

Understanding f(x) and y in the function f(x) = x² + 4: Explained

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Understanding f(x) and y in the function f(x) = x² + 4: Explained

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