# Holiday Bulb (AR Modeling Challenge)

- Author:
- Tim Brzezinski

- Topic:
- Parabola

In this GeoGebra Augmented Reality modeling challenge, the goal here is to author 2 surface equations (with domain restrictions) to model the holiday bulb seen in the screencast below.

**Modeling Clues:**1) Both surfaces are paraboloids of revolution (where cross sections parallel to the xy-plane are circles). 2) The**blue surface**has vertex (0,0,5). The**pink surface**has vertex (0, 0, -3). 3) Both surfaces meet on the xy-plane itself (with no overlap). 4) The point (-1, 1, 3.4) lies on the blue surface.**Additional Challenge**: As you can see from the screencast, these 2 surfaces better model this surface at the upper and lower ends vs. the lower-middle (where it's widest). What other quadric surface model(s) could we use to better model these holiday bulbs?