In a function, each input (or domain element) must map to exactly one output (or range element).
In the relation provided:
- For input 4, the output is 1.
- For input 3, the output is 1.
- For input 2, the output is 4.
- For input 1, the output is 4.
Here, the inputs 2 and 1 both map to the output 4, which is allowed. However, the main criterion for a function is that no input should map to more than one output.
In this case, each input maps to a single output:
- Inputs 4 and 3 map to different outputs.
- Inputs 2 and 1 also map to different outputs.
Since each input maps to one output and no input shares different outputs, we can conclude that this relation is not a function.
Therefore, the correct option is:
Option 2: the relation is not a function.