Answer
$f'(x)=\frac{-1}{x^2}$
$f''(x)=\frac{2}{x^3}$
$f'''(x)=\frac{-6}{x^4}$
Work Step by Step
$f(x)=\frac{1}{x}=x^{-1}$
Using Power Rule:
$f'(x) = -x^{-2}=\frac{-1}{x^2}$
$f''(x) = 2x^{-3}=\frac{2}{x^3}$
$f'''(x) = -6x^{-4}=\frac{-6}{x^4}$