PLOT 3D of laplacian of a FUNCTION

I WANT TO PLOT LAPLACIAN(-((X^2)+(Y^2)))

syms x y
r(x,y) = -(x.^2 + y.^2) ;

 f(x,y)=laplace(r);

HOW TO PLOT IT 3D

[Star Strider]

Use the laplacian function.

The laplace function calculates the Laplace transform.

[Roger Stafford]

It wouldn't be a very interesting plot. The Laplacian is a constant -4 for all x and y.