Hi

In the picture below, ignore the part I crossed out with red. How did they get the -1/v

^{2} (underlined in blue)? Could it have been from the g'(x) above? I still can't see how the writer got it.

If I use chain rule to differentiate u/v,

d/dx (u/v) = u*dv/dx + (1/v)*du/dx