A Function or Not?

Walagaster

MHF Helper
Apr 2018
223
144
Tempe, AZ
Yes. It is not a function.
 

Walagaster

MHF Helper
Apr 2018
223
144
Tempe, AZ
Yes. For example, if $x=0$ you get two values for $y = \pm \sqrt 3$. That's all you need to contradict being a function.