Note: I have listed good problems for practice as "Do these problems". You only need to hand in the problems labeled "To turn in".
Exercises from Section 2.1 page 39-41: Do these problems: 6,13,15,17,21,31,34,35. To turn in: 6, 15, 21, 31, 34, 35 Comments: #6: use a computer to draw the direction field for part a). #21: use a computer to draw the direction field for you. Use screen capture to create your printout for both of these problems. Answer the questions in part a) with words. #34,35: These are "backward problems". We try to find the ODE that gives the desired solutions instead of finding the solution to the ODE. One approach is to look through previous problems to find similar solution behavior and the tweak the problem to get these exact behaviors. Another is to try to think about what y' should be when y is the desired long term solution. Then make sure y' is the right size on either side of that long term behavior so that all solutions tend toward that long term solution.
Exercises from Section 2.2 page 47-50: Do these problems: 8,10,12,21,23,26,30. To turn in: 8, 10ac, 21, 23, 30a-e Comments: #21: In the hint, "integral curve" just means "trajectory" so the hint says to look for values where y' is infinite(doesn't exist). #30: Parts b) and c) are closely linked here so if you have trouble with what b) is asking look at c). Also for c) show that the second equation is obtained from the first equation.
Exercises from Section 2.3 page 59-68: Do these problems: 9, 10, 14 To turn in: 14a
Exercises from Section 2.4 page 75-77: Do these problems: 2,8,13,22,24,25,26,28,32. To turn in: 13, 22, 24, 28 Comments: #28: This problem clearly depends on #27, so read through that. The solution method is essentially a u-substitution but for an ODE instead of an integral. We are changing variables from y to v (don't forget to find y' in terms of v' also). The resulting ODE for v should be linear (as 27b suggests).
This extra problem should be turned in with the others. The equation dy/dt = 1/(1+y), with initial condition y(0)=-1 has two solutions. a) Find both solutions analytically. Now solve the system using a computer (e.g. the ODE solver by some good folks at University of Applied Sciences, Dresden Germany.) The computer will compute dy/dt to be Inf (infinity) so you will have to start close to -1 but not at it to even get a numerical solution. (Answer with a paragraph using complete sentences. You don't need to hand in the pictures.) b) Which solution does the computer find? c) How can you trick the computer into finding both solutions?