How to graph an elipsoid of the type w=f(x,y,z)=X*X/9 + Y*Y/16 +Z*Z/25
Your w needs a numerical value but you can do it with the Wolfram|Alpha calculator.
http://www.wolframalpha.com/input/?i=x%5E2%2F9%2By%5E2%2F16%2Bz%5E2%2F25%3D1