1. The problem statement, all variables and given/known data Hello all. The question asked here is to find the point on the surface: z2 - xy = 1 that is closest to the origin. 3. The attempt at a solution I only have experience in doing this with 2 variables. I begin by trying to find "d", I get that d = sqrt[...] but I have three variables to deal with. I end up with d2 = (z2-1)/y + (z2-1)/x + xy + 1 The problem is that the partial derivatives with respect to x, y and z are quite messy and they don't look right... Does this look correct so far? Thanks all!