30.11 Chapter 4, Linear Second-Order Equations. EXERCISES 4.1 at page 156

30.11.1 problem 1
30.11.2 problem 2
30.11.3 problem 3
30.11.4 problem 4
30.11.5 problem 5
30.11.6 problem 6
30.11.7 problem 7
30.11.8 problem 8
30.11.9 problem 9
30.11.10 problem 10 (a)
30.11.11 problem 10 (b)
30.11.12 problem 10 (c)