[x, y] = meshgrid(linspace(-2, 2, 101), linspace(-2, 2, 101));
z = (x.^2).*(y.^2) - x.*y + x + 2*y -2;
ind = find((z>2) & (x<0));
plot3(x(ind), y(ind), z(ind), 'ro');
xlabel('x');
ylabel('y');
zlabel('z');