Answer
Elliptical paraboloid.
Work Step by Step
Rewrite as
$\displaystyle \frac{z-8}{-1}=\frac{x^{2}}{1^{2}}+\frac{y^{2}}{1^{2}}$
We compare with Table 12.1 and conclude that this is an elliptical paraboloid.
It opens down and the vertex is raised up 8 units (from the origin).
The traces in xz and yz planes are parabolas.
The traces in planes parallel to the xy plane are circles (special case of ellipses).
