Question

Which relation is a function?

{0, –9, –2, –3}
{(0, –9), (–9, –2), (0, –3)}
{(0, –9), (–2, –3), (–2, 0), (–3, –2)}
{(0, –9), (–9, 0), (–3, –3)}

Answer 1

The last option is a function as no x-values repeat!

Answer 2

Last on - I think
{0,-9), (-9,0), (-3,-3)}