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Math Help - how can I tell whether an equation is a function or not

  1. #1
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    how can I tell whether an equation is a function or not

    hello everybody

    I would like to know how can I know whether an equation is a function or not

    for example x^2+y^2= 9 , I know this is not a function because it doesn't pass the vertical line test, but is any way to tell algebraically if its a function or not?
    thank you.
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  2. #2
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    Quote Originally Posted by jhonwashington View Post
    hello everybody

    I would like to know how can I know whether an equation is a function or not

    for example x^2+y^2= 9 , I know this is not a function because it doesn't pass the vertical line test, but is any way to tell algebraically if its a function or not?
    thank you.
    It means,
    "Can for the same value of x be two distint values of y (at least)"
    The answer is yes.

    Consider,
    x=1
    We have,
    y=sqrt(8) and y=-sqrt(8)
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