Hello

I have two functions:

and

As someone might guess, this is a optimization problem of sorts (minimization of A(x,h) with V(x,h)=4 as constraint). My problem arises when I attempt doing partial differentiation, and the root of the problem is perhaps that I have forgotten something.

When, for instance, I take the partial derivatives of A(x,h), I get this:

It doesn't seem right, and I think that the problem is the thing with variables multiplied by eachother. Can someone please point me in the right direction with this?