Answer:
For a single value of x function has more than one corresponding value of y which satisfies the equation.
Step-by-step explanation:
Function: A relationship between a set of inputs and a set of possible outputs, where exactly one output is associated with each input.
It means for an equation to represent a function any single value of x there should be only one corresponding value of y which satisfies the equation.
Now consider the given equation.
[tex]x^2 + y^2 = 8[/tex]
If we put x=0 then we get two value of y i.e [tex]\sqrt8[/tex] and [tex]-\sqrt8[/tex] which satisfy the equation and therefore the equation is not a function.