Math 81 Sample Exam 2

Some Sample Exam Questions for the Second 81 Exam

Dr. Cleary

1) Give an example of a first-order differential equation which has more than one solution for an initial value problem. Are there any second-order differential equations that also have this property?

2) Set up the Picard iteration technique to solve the initial value problem
and do the first two iterations.

3) On what interval is the solution of with initial condition
guaranteed by our 1st order existence theorem?

4) For what initial conditions can we guarrantee uniqueness of solution for the differential equation of question 3?

5) Is the following set of functions a basis for the solutions to the second order equation: : ? If not, find such a basis.

6) Is the following a basis for the solutions to the second order differential equation
: ? If not, find such a basis.

7) Solve the differential equation .

8) Find all complex 4th roots of 8 - 6i.

9) How many of the solutions to have ?

10) Compute the Wronskian of the set . Is it a linearly independent set?

11) Find a basis for the solutions to

12) Find the general solution to the differential equation

13) An underdamped mass-spring system is set into motion. If the mass starts at 10 cm above the rest position and has a downward push of 5 cm/sec, draw a sketch of the resulting motion.

14) Solve the differential equation :

15) Solve the differential equation subject to the conditions that y(0) = 4 and y(10) = -1.

15) Prove the following or give an example to show that it is false: For any complex number z, .

16) Find another independent solution to the equation given that we notice the ``obvious'' solution of .

17) Find the general solution to

18) Find the general solution to

19) Sketch the output of the following Mathematica code:

Do[sol[i]= DSolve[{y''[x]-2 y'[x] + y[x] == 0, y[0]==10, y'[0] == i*10},
                    y[x],x] [[1,1,2]],{i,-4,4}]

Plot[Evaluate[Table[sol[n],{n,-4,4}]],{x,0,2}]

20) Solve the following differential equation: by introducing a new variable and eliminating .



Sean Cleary
Thu Mar 20 10:15:59 PST 1997