Answer:  
 
 
Explanation:
 Given the linear function f(x):
 
 
 
 By definition. a relation is a function if each input value has only one output value. In this case you need to find the output value for the input value 
 . In order to do this, you need to substitute this value of the variable "x" into the linear function given.
. In order to do this, you need to substitute this value of the variable "x" into the linear function given.
 Then:
 When 
 :
:
 
 
 
 Remember the multiplication of signs:
 

 Then, the value of f(x) when 
 is:
 is:
 
 
 
 
