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

[thomas49th]

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]

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]

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 x^2+ 4.

No, that is NOT the same as saying "y= x^2+ 4" 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.