questao1.m

f = figure;
global a
global b
if isempty(a)
    a=1;
end
if isempty(b)
    b=1;
end
slider1 = uicontrol('Parent',f,'Style','slider','Position',[81,65,419,23],...
              'value',1, 'min',0, 'max',10);
bgcolor = f.Color;
            
slider2 = uicontrol('Parent',f,'Style','slider','Position',[550,65,419,23],...
              'value',1, 'min',0, 'max',10);
            
slider1.Callback = @(es,ed) slider_plot(es, ed, get(es,'value'), b, f); 
slider2.Callback = @(es,ed) slider_plot(es, ed, a, get(es,'value'), f); 

slider_plot.m

function slider_plot(es, ed, alpha, beta, f)
global a
global b
display(alpha)
display(beta)
a = alpha;
b=beta;
x1 = linspace(-3,3,50);
x2 = linspace(-3,3,50);
[x1,x2] = meshgrid(x1,x2);
x1p = -x1 - x2.*x2.*x2;
x2p = x1;

quiver(x1,x2,x1p,x2p,5);
hold on

x1 = linspace(-3,3,1000);
x2 = linspace(-3,3,1000);
[x1,x2] = meshgrid(x1,x2);

V = 4*a*x1.*x1.*x1+2*b*x1+x2;
Vponto = -4*a*x1.*x1.*x1.*x1+(1-2*b)*x1.*x1+x1.*x2-4*a*x1.*x1.*x1.*x2.*x2.*x2-2*b*x1.*x2.*x2.*x2-x2.*x2.*x2.*x2 ;
%V = 4*a*x1.*x1.*x1+2*b*x1+x2;
%Vponto = (4*a-2)*x1.*x1.*x1.*x2+(2*b-1)*x1.*x2-x2.*x2-x1.*x1.*x1.*x1;
colormap(colorcube)
contour(x1,x2,Vponto<0,1, 'LineWidth',4)
colormap(hot)

contour(x1,x2,V,100)



axis([-3 3 -3 3])
hold off
    
end