69.31 Chapter 3 (Systems of differential equations). Section 23.2 The method of undetermined coefficients. Exercises page 239

69.31.1 problem 815
69.31.2 problem 816
69.31.3 problem 817
69.31.4 problem 818
69.31.5 problem 819
69.31.6 problem 820
69.31.7 problem 821
69.31.8 problem 822
69.31.9 problem 823
69.31.10 problem 824