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Very quick question

  1. Jan 3, 2008 #1
    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???
  2. jcsd
  3. Jan 3, 2008 #2
    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.
  4. Jan 4, 2008 #3


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    Staff Emeritus
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    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.
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