\( \definecolor{colordef}{RGB}{249,49,84} \definecolor{colorprop}{RGB}{18,102,241} \)
Show that \(f : \mathbb{R}^* \to \mathbb{R}\), \(f(x) = 1/x\), is differentiable at every \(a \in \mathbb{R}^*\) from the difference quotient.
Capture an image of your work. AI teacher feedback takes approximately 10 seconds.