Why Do I Keep Getting the Wrong Answer in My Differential Equations Problem?

[mr_coffee]

Look whos back! I ran into another problem, i redid the problem twice and i keep coming out with the same answer!
here is what i have:
http://img139.imageshack.us/img139/6205/lastscan5qw.jpg
This is what I submitted which was wrong:
http://cwcsrv11.cwc.psu.edu/webwork2_files/tmp/equations/d3/290d3b430db500dfaef04358236c001.png
This is what
Thanks!

 

[Pseudo Statistic]

If you're having trouble doing it with sine and cosine, do it the old fashioned Ae^r1x + Be^r2x way using the complex roots. (It's an alternative method and chances are you'll make less mistakes)

 

[HallsofIvy]

If that is what you actually submitted, you might want to compare it closely to your handwritten answer- do you notice some missing parentheses?

 

[mr_coffee]

Pseudo, this program that evaluates the expressions tells us to not use that form because it won't evaluate complex expressions inside the e^, so I have to use sin/cos. :(

Thanks i didn't catch that halls but it still told me, do not pass go, do not collect 200 dollars. I think i shall e-mail the professor and see if its corrrect and the program might just b f'ed up.
http://cwcsrv11.cwc.psu.edu/webwork2_files/tmp/equations/3d/4a14ab68c9143ae5c68ed8af6e5ba91.png

 

[assyrian_77]

Again, like last time, your differentiation is wrong! You seem to forget that there is a fraction in the exponential; your didn't include the denominator (1000) in the differentiation! It is the exact same mistake you did last time. I suggest you carefully go through the differentiation again.

 

[mr_coffee]

Okay i redid it, I'm not sure if its right t hough because the webhomeworks happen to be down. but this is what I got:
http://img212.imageshack.us/img212/6735/lastscan1rm.jpg

 

[assyrian_77]

I ended up with the equation

$$7=\frac{14}{1000}-\frac{\sqrt{2951}}{1000}B$$

so B should be

$$B=-\frac{6896}{\sqrt{2951}}$$

However, I could have made a mistake.

 

[mr_coffee]

Hm...I tried my answer and your answer, switching the signs as well but can't seem to get it right.
http://cwcsrv11.cwc.psu.edu/webwork2_files/tmp/equations/02/a1ed9e2620a00e5df238eb7b1954831.png