`f(x) = (x-4)/(x+4)`

`f'(x) = {(x+4) - (x-4)}/(x+4)^2`

`or, f'(x) = 8/(x+4)^2`

`thus, f'(c) = f'(3) = 8/(3+4)^2`

`or, f'(c) = f'(3) = 8/7^2 = 8/49`

``

`f(x) = (x-4)/(x+4)`

`f'(x) = {(x+4) - (x-4)}/(x+4)^2`

`or, f'(x) = 8/(x+4)^2`

`thus, f'(c) = f'(3) = 8/(3+4)^2`

`or, f'(c) = f'(3) = 8/7^2 = 8/49`

``