Says

The original equation is

So for the first derivative with respect to x ,I used the product rule on first part then the quotient rule on second part to get the derivative below.

Then for this one I just had to differentiate with respect to y which made it this.

However i want to find

But i dont quite understand what it means , and the answers i get do not match each other according to youngs theorum.

Any suggestions?

Youngs theorum =