Question

What value(s) of x in the relation below would create a set of ordered pairs that is not a function? Justify your answer. {(0,5) (1,5) (2, 6) (x, 7)}

Answer 1

First, let's see the points on the coordinate plane:

Now, let's remember that a function has every element of it's domain related with only one element from it's image.

Therefore, x = 2 would create a set of ordered pairs that is not a function. Let's see it in the plane:

As we can see, x = 2 has two values on the image: f(2) = 6 and f(2) = 7, and this never can happen in a function.