MATLAB: How to write an expression like this question in matlab codes and execute it without errors but logical answers

finding volumeMATLAB

Using double integral.Find the volume of the solid lying under the elliptic paraboloid x2/4+y2/9+ z = 1 and above the rectangle R = [−1,1]×[−2,2]

Try the following script

close all
clearvars
syms x y z
z=-(x^2)/4 - (y^2)/9 +1
fsurf(z); 
xlabel('x'); ylabel('y'); zlabel('z');
vol= int( int(z, x, -1, 1  ) , y, -2, 2)

If you run it, it would give something like this:

syms x y f(t)
d = sqrt(f(x)^2+f(y)^2)
d = 
simplify(diff(d,x) + diff(d,y))
ans =

How about:

syms x y z;
[x,y]=meshgrid(-10:1:10);
z = abs(sqrt(9-x.^2));
surf(x,y,z);
ylim([-1 2])