Find all level sets of the function:
f(x,y,z) = x^2 + y^2 - z^2
If is a fixed number, the level sets of at level consists of all points in which are solution of the equation . If the level surface is a cone centered at the origin opening along the z axis. If , then the level surface is a hyperboloid of one sheet. Finally, if , the level surface is a hyperboloid of two sheets.