18 Chapter 4, Linear Systems. Exercises page 190

 18.1 problem 2(a)
 18.2 problem 2(b)
 18.3 problem 2(c)
 18.4 problem 2(d)
 18.5 problem 3(a)
 18.6 problem 3(b)
 18.7 problem 3(c)
 18.8 problem 3(d)