Answer:

Explanation:
The given equation is 
 
where, b is the input value and a is the output value of function f. 
We need to find the formula for f(b) in terms of b. 
It means we have to separate 
 on one side because 
. 
Consider the given equation. 
 
Subtract 7b from both sides. 
 
 
Divide both sides by 4. 
 
Substitute a=f(b). 
 
Therefore, the required formula is 
.