Let $$ be the surface defined by the equation $3^2+6^2=1$.
Determine the range of values of $x$ for which the $x$-traces (cross-sections) are non-empty. That is, find all $$ such that the system of equations $3^2+6^2=1,\,=a$ has a solution. In addition, choose the correct general description for the traces from the list.
Repeat for the $$- and $z$-traces. The $$ traces are (lines, ellipses, hyperbolas, parabolas?) and are non-empty for $y$ in the range: