Question

How do you decide whether the relation `2x^2+7y^2=1` defines a function?

Answer 1

not a function

Explanation:

`2 x^2 + 7 y^2 = 1`
`7y^2 = 1 - 2 x^2`
`y^2 = (1 - 2 x^2)/7`
`y = +- sqrt((1 - 2 x^2)/7)`

it is not a function because one value of `x` has more than one value of `y`. It means one domain has more than one codomain. Function must has one-to-one or more-to-one relations only.