13.10 Section 2.4, The method of variation of parameters. Page 154

13.10.1 problem 1
13.10.2 problem 2
13.10.3 problem 3
13.10.4 problem 4
13.10.5 problem 5
13.10.6 problem 6
13.10.7 problem 7
13.10.8 problem 8
13.10.9 problem 11
13.10.10 problem 12