Question 1121070
<br>
A relation is NOT a function if there are two (or more) different outputs for the same input.<br>
The given function is f: {(1,a),(2,a),(3,d),(4,c)}.  The inputs are all different, so there is no possibility that there are different outputs for the same input.<br>
Therefore f is a function.<br>
The inverse function is f^-1: {(a,1),(a,2),(d,3),(c,4)}.  Input a has two different outputs (1 and 2); therefore f^-1 is not a function.