Given:
4 relations in the options.
To find:
The relation which represents a function.
Solution:
We know that, a relation is a function if there exist a unique output value for each input value.
In option A, we have two output values y=-5 and y=1 for single input value x=-1. So, it is not a function.
In option B, we have two output values y=2 and y=4 for single input value x=3. So, it is not a function.
In option C, we have two output values y=1 and y=7 for single input value x=-1. So, it is not a function.
In option D, we have unique output value for each input value. So, it is a function.
Therefore, the correct option is D.
