%prova
clear
x=0:0.05:1;
a=10;
b=10;
y=(a-b*x).*x;
[dm1 dm2]=size(x);
mov = avifile('mov2.avi')
for i=1:dm2
    plot(x,y,':');
    hold on
    plot(x(i),y(i),'sr');
    F(i)=getframe(gca);
    mov = addframe(mov,F(i));
    hold off
end
movie(F,2);
