Answer
(a) $\frac{1}{x+h}$
(b) $\frac{-h}{x(x+h)}$
(c) $\frac{-1}{x(x+h)}$
Work Step by Step
(a) Given $f(x)=\frac{1}{x}$, we have $f(x+h)=\frac{1}{x+h}$
(b) $f(x+h)-f(x)=\frac{1}{x+h}-\frac{1}{x}=\frac{x-(x+h)}{x(x+h)}=\frac{-h}{x(x+h)}$
(c) $\frac{f(x+h)-f(x)}{h}=\frac{-1}{x(x+h)}$
