72.9 Chapter 3. Second order linear equations. Section 14. Introduction. Problems at page 112

72.9.1 problem 1 (a and b)
72.9.2 problem 2
72.9.3 problem 3 (a and b)
72.9.4 problem 4 (a)
72.9.5 problem 4 (b)
72.9.6 problem 4 (c)
72.9.7 problem 5 (a)
72.9.8 problem 5 (b)
72.9.9 problem 5 (c)
72.9.10 problem 5 (d)
72.9.11 problem 5 (e)
72.9.12 problem 7
72.9.13 problem 8