derivatives

Question

Find the derivative of f(x) =  at x = 6.

Answer 1

f(x) =-9/x

      =-9x^-1

Using the formula:d/dx(x^n) =nx^(n-1)

f'(x) =-9 d/dx(x^-1)

       =-9(-1x^(-1-1))

       =9 x^-2

       =9/x^2

At x=6

f'(6) =9/6^2

        =9/36

       =1/4

f'(6) =1/4