Question

need help please~ I have an assignment due at 4 pm today

Answer 1

have you made any progress at on it?

Answer 2

(sidenote: as A>0, it would be nice to consider dA²/dx if the question didn't instruct us otherwise >_<)

Answer 3

I dont understand what #1 question is asking?

Answer 4

For the first part - finding dA/dx? Consider U = xy for example. If you differentiate U with respect to x, applying the product rule and noting d/dx of y = dy/dx, you get something of a similar form to what you're looking for:
dU/dx = y + x dy/dx

Answer 5

Further, if you perform implicit differentiation on the second relationship given, you should be able to get a substitution for dy/dx as a function of x and y.