Is #x^2+y^2=9# a function?

1 Answer
Alan P.
Aug 1, 2015

#x^2+y^2 = 9# is not a function

Explanation:

In order for an equation to represent a function any single value of #x# must have at most one corresponding value of #y# which satisfies the equation.

For #x^2+y^2=9#
#color(white)("XXXX")#if (for example) #x=0#
#color(white)("XXXX")#there are two values for #y# (namely #+3# and #-3#) which satisfy the equation

and therefore the equation is not a function.

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