<li>Is y=the square root of x-7 (sorry that I cannot type the mathematical equation with the keyboard) a function? My sohomore math teacher told me that for an equation to be a function, the equation must pass the vertical line test or that the x-value corresponds to only one value. But today, my precal teacher told me that for an equation to be a function, the equation must pass the vertical line test and that all x-values must be used. In class, my precal teacher said that the equation given above is not a function because if you let 0<x<6 (I am only concerning integers for now), the equation would become imaginary? Is the equation a function or not?</li>
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<p>It is definitely a function, as long as it is not y = +/- (x-7)^(1/2). Its domain is just restricted.</p>