Question

Select the sets that are not functions.

O A = {(1, 2), (2, 3), (3, 4), (4,5)}
B = {(1, 2), (2,1),(3.0)(4, -1)}
O C = {(-1,3), (0, 3), (1, 3), (2,3)}
ID = {(1, 1), (1, 2), (1, 3), (1,4)}
E = {(6,2), (7,3), (6, -1), (5,4)}

Answer 1

ID and E are not functions. For a set to be a function, every x value must have only one output. In ID we can see 1 has multiple outputs, and in E we can see 6 has two different outputs.
It is important to note that it’s okay for a function to have the same y values with different x values. But a function CANNOT have an x value with multiple different y values related to it.
Wether you think of it in terms of x and y, or input and output, this rule still applies.

Answer 2

ID={(1, 1), (1, 2), (1, 3), (1, 4)}
E={(6,2), (7,3), (6,-1), (5,4)}