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| Question 174588:  I am very unsure when it comes to functions.  Can you please help me to understand what makes something a function?  Here is the question.
 Which of the following are functions?  Explain why/why not.
 A.  f(x)=2 if x>1 otherwise f(x)=-1
 B.  f(x)=5 if x>0 or f(x)=-5 if x<0 or f(x)=5 or -5 if x=0
 C.  f(x)=x/10
 Any help I recieve would be greatly appreciated as I am so utterly confused.
 Answer by stanbon(75887)
      (Show Source): 
You can put this solution on YOUR website! A function is a set of ordered pairs with the following restriction: Each x value must have only one y value
 associated with it.
 ====================================
 Which of the following are functions? Explain why/why not.
 A. f(x)=2 if x>1 otherwise f(x)=-1
 This is a function.  Choose any value of x and the corresponding
 y value will be 2 if x>1, or it will be -1 if x<=1
 But each x value will have only one corresponding y value.
 --------------------------------------------------------------
 B. f(x)=5 if x>0 or f(x)=-5 if x<0 or f(x)=5 or -5 if x=0
 Not a function because you have two points (0,5) and (0,-5)
 Notice that x=0 has two associated y values, so not a function.
 ---------------------------------------------------------------
 C. f(x)=x/10
 This is a function; each x value has one y value associated with it.
 =========================
 Cheers,
 Stan H.
 
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