From the table, it can be observed that corresponding to x = -1, the value of y is 2.
Relation is a function if there exist only one oputput for every input.
So if ordered pair (-1,4) is included in the table, then relation give 4 and 2 as output for same input of x = -1. Thus this violates the condition of relation to be a function.
In table there is not output value for x = 4. So if ordered pair (4,-1) is include in the table then relation is a function.
Thus ordered pair (-1,4) is included in table then relation is no longer a function.