Answer:
Hyperbola.
Step-by-step explanation:
We start from the function:
[tex]x^{2} +y^{2} -z^{2} =36[/tex]
We may get the traces if we cut the surface in planes x=k. This is equivalent to replace x for k:
[tex]k^{2}+y^{2} -z^{2}=36\\y^{2} -z^{2}=36-k^{2}[/tex]
The last equation is the equation of an hyperbola, which varies its characteristics depending on K (the plane cut).