# Functions that are defined by the equation [closed]

How many different functions of $x$ are defined by the equation $x^2+y^2=9$ if the domain is $x\in [-2,2]$?

(A) None

(B) 1

(C) 2

(D) 4

Need help finding out how many functions are defined by the equation.

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## closed as off-topic by user7530, David, Hakim, le gâteau au fromage, Weapon of ChoiceJul 1 at 3:55

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Any ideas here? Any guesses? Have you tried anything on your own? –  Omnomnomnom Jul 1 at 1:38
There are infinitely many possibilities. But they probably want you to choose (C). –  André Nicolas Jul 1 at 1:42
@GitGud: consider any function of the form $f(x)g(x)$ where $f(x)$ is one of the semicircles and $g(x)$ takes the values $1$ and $-1$. If they specified continuity, then (C) would indeed be correct. –  Omnomnomnom Jul 1 at 1:45
Weird question. In the interval, the equation does not define a function. –  André Nicolas Jul 1 at 1:49
This is an example of bad written question, where you need to answer to the "spirit of the question" (what the teacher had in mind) more than the actual question. –  Taladris Jul 1 at 2:02