Question

Which of the following relations is a function?

{(-4, 3), (-4, 2), (1, 9), (6, 7)}
{(-4, 3), (-2, 0), (2, 7), (3, 9)}
{(2, 1), (4, 2), (2, 3), (8, 4)}
{(0, 0), (0, 1), (2, 3), (4, 5)}

Answer 1

an function does not have an (x,y) pair where the x is the same, but the y is different
example: if you see (0,0) and (0,1) that is *not* a function.
so look for (x,y) that have the same first number. then look at the second number.
if they are different, you do not have a function.