It is the property of every function that every input to the function from its domain must have a unique image in the range of the function
Thus:
The same input to a function CANNOT have different outputs/images
For this reason, the value of k:
- CANNOT be 1, since the input value 1 already has an image (output) value of 2
- CANNOT be 3, since the input value 3 already has an image (output) value of 2
- CANNOT be 4, since the input value 4 already has an image (output) value of -5
CAN ONLY be -9 , since the input value -9 already has an image (output) value of 2