how to plot the gradient of a equation having specific region?

hello i have the equation

f(x,y)=-5x^3+4yx+6y^3+1

the gradient with respect to x is

f(x)=-15*x^3+4*y

how to plot the gradient having area

-2<x<2, -2<y<2

Answer 1

[Torsten]

x = -2:0.1:2;
y = x;
[X,Y] = meshgrid(x,y);
f = @(x,y) -15*x.^2+4*y;
surf(X,Y,f(X,Y))

Answer 2

[Star Strider]

Perhaps this —

syms x y 
f(x,y)=-5*x^3+4*y*x+6*y^3+1

f(x, y) = 

Gf = gradient(f,x)

Gf(x, y) = 

figure
fsurf(Gf, [-2  2    -2  2])
xlabel('X')
ylabel('Y')

.