function [ dxdt ] = kolZad1(t,x )

u = pobuda(t);
k = 0.5;
e = u-k;


dxdt = [x(2)
        4*e-x(1)-x(2)
        x(4)
        x(1).^2-x(3)];
end

/////////////////////////////////
-- pobuda(t)

function out = pobuda(t)

out = ((-1/3)*t + 3).*((t>=1 & t<=3) | (t>=4 & t<=6) | (t>=7 & t<9));

end