Medal & Fan. Help.?!

Which relation is a function?

{(1, 2); (2, 3); (3, 4); (1, 5)}
{(1, 2); (1, 3); (1, 4); (1, 5)}
{(1, 2); (2, 3); (3, 4); (2, 5)}
{(1, 2); (2, 2); (3, 2); (4, 2)}

Question

Medal & Fan. Help.?!


  Which relation is a function?

   
       {(1, 2); (2, 3); (3, 4); (1, 5)}
        {(1, 2); (1, 3); (1, 4); (1, 5)}
        {(1, 2); (2, 3); (3, 4); (2, 5)}
        {(1, 2); (2, 2); (3, 2); (4, 2)}

studygurl14 · Answer

A coordinate is set up like this (x,y), x being the input, y being the output. A function cannot have one input (x-value) result in more than one output (y-value). Look at the answer choices. Are there any coordinates that have the same x-value with different y-values?