Ejercicio 3

function sistema
[t1, xx1]=ode45(@resorte, [0 40], [1 0], [ ], 5);
plot(t1, xx1(:,1))
hold on
[t2, xx2]=ode45(@resorte, [0 40], [1 0], [ ], 40);
plot(t2, xx2(:,1))
[t3, xx3]=ode45(@resorte, [0 40], [1 0], [ ], 200);
plot(t3, xx3(:,1))

function x=resorte(t, x, c)
x=[x(2); (-c*x(2)-20*x(1))/20];