function instability(f,trange,y0,h)
a=trange(1); b=trange(2);

[t,y]=eul(f,[a,b],y0,h);
%[t,y]=rk2(f,[a,b],y0,h);
%[t,y]=rk4(f,[a,b],y0,h);
plot(t,y)
legend(['stepsize=',num2str(h),'.'])
shg