Consider the function $f(x) = 4x-x^{2}$.

Use the limit definition to compute the following derivative values:
$f'(0) =$
$f'(1) =$
$f'(2) =$
$f'(3) =$

Observe that the work to find $f(a)$ is the same, regardless of the value of $a$. Based on your work in the first part, what do you conjecture is the value of $f'(4)$?
$f'(4) =$
How about $f'(5)$?
$f'(5) =$
(Note: you should not use the limit definition of the derivative to find either value.)