% Problem 7.9
z=-1;
p=[0 0 -6 -1.5 (-4.0000 +15.4919i) (-4.0000 -15.4919i)];
[num,den]=zp2tf(z,p,1);
printsys(num,den)
rlocus(num,den)
axis([-10 2 -20 20])
grid