85.86 Chapter 10. Systems of differential equations and their applications. A Exercises at page 491

85.86.1 problem 1 (a)
85.86.2 problem 1 (b)
85.86.3 problem 1 (c)
85.86.4 problem 1 (d)
85.86.5 problem 2 (a)
85.86.6 problem 2 (b)
85.86.7 problem 3