#!/usr/bin/python
## 4.11

import scipy as sp
from scipy import signal

num = sp.array([11,-15,6])
den = signal.convolve([1,-2],signal.convolve([1,-1],[1,-1]))
u = sp.zeros(5)
u[0] = 1
y = signal.lfilter(num,den,u)

print num, den

#Plot of impulse response???