Answer: 

Explanation:
The given arithmetic sequence : 3, 7, 11, 15...
Here , the first term = 

Common difference =

We know that function represents any Arithmetic sequence is given by :-
 , where n= Number of term= 1,2,3,4....
 , where n= Number of term= 1,2,3,4....
 is the first term.
 is the first term.
d= common difference.
For the given sequence , the function would be :-

Hence, the function represents the given arithmetic sequence :
