1. The problem statement, all variables and given/known data f(x,y,z)=(xy+yz+xz)/(1+x^2+y^2+z^2) Explain why f has no absolute maximum or minimum. How about critical points? 2. Relevant equations Hint: it is simplest to make 3 cases: a) x+y+z does not =0 b) x+y+z=0 c) x=y=z=0 3. The attempt at a solution I did cases b and c, but I'm not sure how to go about doing a. Also, I'm not sure how to explain why the function does not have an absolute max or min.