I've been trying to solve a quite complex equation using both the chain rule and the quotient rule of differentiation. I think I have a handle on the first part of the equation (the top row), but please see the attached document with my full working and verify that I am correct. Secondly, I am unsure how to proceed with solving the equation after that, since I have to manipulate the (bottom squared) part and I am unsure whether I need to expand using chain rule, or simply expand. So any help solving this problem will be much appreciated!

Here is the attached full workings:

As you can see, I now need to work with the (bottom squared) portion of the equation. I am unsure how to proceed.

Many thanks,

Nathaniel