Describe IN WORDS the surface z=4-abs(x)-abs(y)

I am having trouble describing in words the surface created by the function z = 4 - abs(x) - abs(y).

I know exactly what it look likes. It is plane with a high point at (0,0,4), with "creases" along the x = 0 and y = 0.

Can anyone suggest the correct "mathematical defintion" of the surface? I dont think "creases" is exactly the mathematical term they wish me to use.

Many thanks for any help.

Tammy

Re: Describe IN WORDS the surface z=4-abs(x)-abs(y)

Hi tammyl! :)

Description 1: The surface consists of 4 symmetrically placed planes that intersect at the high point (0,0,4) where it is bounded.

Description 2: It's a pyramid without a bottom.