Answer/Step-by-step explanation:
First, take note of the following:
1. In a function, there can only be one exact range value (y-value) assigned to every domain value (x-value). This means, every x-value in a function has only one possible y-value.
2. In a function, however, a range value (y-value) can be assigned to more than one domain value (x-value). That is two x-values can have the same y-value assigned to them.
Bearing this in mind, let's analyse the examples given to determine whether they represent a function or not.
Example 1: it represents a function, because no x-value has more than 1 corresponding y-value, however, two x-values have the same y-value assigned to them.
Example 2: this does not represent a function because, each x-value has more than one y-value assigned to them.
Example 3: this does not represent a function because one of the x-values, 1, has two y-values, -1.8 and 1.8, assigned to it.