If where f is a continuous function find f(4) and f'(4)

use Fundamental therom of Calculus

so I know that I'm going to let

and then differentiate both sides but how do i defferentiate

and it's derivate how do i do that

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Another question with this F.T.C stuff

Use F.T.C find a function and a number c such that

for x>0

So I know i gotta differentiate both sides but how would i find a number C when F.T.C would just eliminate it since derivative of a number is 0