How do you determine whether the inverse is a function

Example: I'm given 4 pairs and they're [(-1,-2),(-3,-2),(-1,-4),(0,6)]
I know that the inverse is [(-2,-1),(-2,-3),(-4,-1),(6,0)] but how do I determine whether the inverse is a function?

Notice that there are two ordered pairs with x-coordinate -2 but different y-coordinates. So it is not a function.

Both (original and inverse ) are not functions, since for the same input there are two different out puts

for example (-1, -2) and (-1, -4) in original and

(-2, -1) and (-2, -3) in inverse

{(-1,-2),(-3,-2),(-1,-4),(0,6)} ir NOT a function since x=-1 has 2 values of y ---> the inverse does not exist