1. The problem statement, all variables and given/known data I have a square 50x50 units. I want to make a pool(box without a lid), and then cut away the corners. The "corner-square" is x^2. What I want is a formula X(v) that gives me the x value needed to get a fixed volume. 2. Relevant equations The V(x) function is base x height, x(50-2x)^2. But i have problems isolating x based on this formula. 3. The attempt at a solution If i try solving it in Maple I get: 25/2 + 1/2sqrt(625-2v) and 25/2 - 1/2sqrt(625-2v) but this makes no sense to me. I've calculated the max volume at x=25/3 to be 250000/27, and the function is only valid from x=0..25. I guess the answers Maple gives me is because it does not know og my 0..25 range, but I dont know how to make that part of the calculation. If the problem is unclear, please say so and I will try to explain better.