Question

Is `x^2 - y^2 = 7` a function?

Answer 1

`x^2-y^2=7` is not a function

Explanation:

`x^2-y^2=7`
could be rearranged as
`color(white)("XXXX")` `y^2 = x^2-7`

So
`color(white)("XXXX")` `y = +-sqrt(x^2-7)`

That is for `x^2 > 7` there is more than one value for `y`
which is contrary to the requirement for an equation to be a function.