Question

Select the relations that are functions.

{(a, 1), (b, 1), (c, 1)}
{(a, a), (a, b), (a, c)}
{(1, a), (2, a), (3, a)}
{(a, a), (b, b), (c, c)}

Answer 1

These are all functions:

{(a, 1), (b, 1), (c, 1)}
{(1, a), (2, a), (3, a)}
{(a, a), (b, b), (c, c)}

This is NOT a function:
{(a, a), (a, b), (a, c)}

Note that for each x-value, there should only be a single y-value for a function.
x = a cannot produce y = a, y = b and y = c all at once.

Answer 2

thanks