9 Section 2.2.2, Equal roots, reduction of order. Page 147

 9.1 problem 1
 9.2 problem 2
 9.3 problem 3
 9.4 problem 4
 9.5 problem 6
 9.6 problem 7
 9.7 problem 10
 9.8 problem 11
 9.9 problem 12
 9.10 problem 13
 9.11 problem 14
 9.12 problem 15
 9.13 problem 16
 9.14 problem 19
 9.15 problem 20