Chapter 4 - Applications of the Derivative - 4.1 Maxima and Minima - 4.1 Exercises - Page 243: 33

(a). $f(x) = \frac{−1}{x^2} − \frac{1}{x} = \frac{−1−x}{x^2}$ , which is never zero on the domain of the function (which is $(0,∞)$). So the function has no critical points. (b). Since there are no critical points, there are no extrema.

See the graph for explanation.