Mathematics, Discrete Mathematics, Programming.
define set X as X = {2, 3, 4} and Y = {a, b}, we could have: f = {(2, a), (3, b), (4, a)} We can see this is valid because the values 2, 3, and 4 in set X are all mapped to just ONE value. In other words, there is no such example where 2 maps to both a AND b. Now let’s try another few examples that