How to graph the function f(x,y)=9 - x^2 - 9*y^2 in 3D

How i can graph the function f(x,y)=9 - x^2 - 9*y^2 in 3D , please help me guys. i am out of ideas

Answer 1

[KSSV]

m = 100 ; n = 100 ; 
x = linspace(0,1,m) ; 
y = linspace(0,1,n) ; 
[X,Y] = meshgrid(x,y) ; 
Z = 9-X.^2-9*Y.^2 ; 
surf(X,Y,Z)