1. The problem statement, all variables and given/known data Find the curve that is the intersection of x-y-z>-10 and x2+y2/4+z2/9=36. 2. Relevant equations 3. The attempt at a solution The best idea I have is to define x as x=y+z-10 and substitute it into the ellipsoid equation to get a function defined by y and z; the trouble is that leaves out the x. I need to define the curve explicitly in terms of three variables as I need to later take the gradient of the curve. Help appreciated. Thanks.