Hi everyone,

this is an exercise from my circuit class, it involves calculus, and I am unsure about how to do it.

Differentiate the following expression with respect to R_{L}:

From the solutions manual it seems like I am supposed to use the quotient rule. This confuses me, because (other than being a noob in math) I know that one of the variables is R, as specified in the exercise, I imagine R_{L}as being "x" in a "normal" differentiation problem. Other than the R_{L}being kind of an "x" I only see constants in this expression, so why would I use the quotient rule? Isn't the quotient rule only for expressions which have two functions divided by each other? Does this mean that V_{TH}is some kind of function?

I will give a picture of the solution too, so that you can take a look at it thank you all for reading!