Answer:
[tex]\Huge \boxed{3a+4}[/tex]
Step-by-step explanation:
The function is given.
[tex]f(x)=3x+1[/tex]
To find : [tex]f(a+1)[/tex]
The input for the function f(x) is (a + 1).
Replace x with (a + 1).
[tex]f(a+1)=3(a+1)+1[/tex]
Expand brackets.
[tex]f(a+1)=3a+3+1[/tex]
Simplifying.
[tex]f(a+1)=3a+4[/tex]
