# Differential Equations - I need Help

• 03-28-2004
KneeGrow
Differential Equations - No more help, I FIGURED OUT THE MISTAKES WOOH
Okay here's a few problems that i've solved, i just need some math wiz to check me on my work. Thanks a lot guys, i really appreciate it!

1. y''' - 4y'' + y' + 6y =0
ANSWER: y=(c1)e^(3X) + (c2)e^(2X) + (c3)e^(-X)

2. 4y''' + 28'' + 61y' + 37y =0
ANSWER: y=(c1)e^(-X) + (c2)e^(-3X)(cos0.5X) + (c3)e^(-3X)(sin0.5X)

3.y'''' - 2y''' + 2y'' -2y' + y =0
ANSWER: y=((c1) + c(2)X)e^X + (c3)e^X(cosX) + (c4)e^X(sinX)

4. 4y''''' - 23 y'''' -33y'' - 17y' - 3y =0
ANSWER: y=(c1)e^(3X) + ((c2) + (c3)X)e^(-X) + ((c4) + (c5)X)e^(-0.5X)

FOR # 5/6 I USED METHOD OF UNDETERMINED COEFIFICENTS FOR NONHOMOGENEOUS DIFF EQ'S

5.y'' - 3y' - 4y = 2sinX
ANSWER: y=(c1)e^(4X) + (c2)e^(-X) + (3/17)cosX - (5/17)sinX

6.y'' - 3y' -4y = 4X^2
ANSWER: y= (c1)e^(4X) + (c2)e^(-X) - (1/8) - (1/4)X^2
• 03-28-2004
Xterria
I hope i never have to do math that hard...
• 03-28-2004
axon
>>I hope i never have to do math that hard...

well if you are going into ANY engineering field you will have to leardn DFQ. KneeGrow, I'll check it out later tonite if I get some spare time.
• 03-28-2004
Xterria
-DAAWEETED!!!!!!-
• 03-28-2004
golfinguy4
You are a loser.
• 03-28-2004
Xterria
huh? what'd i do now?
EDIT
alright i get it..
..i guess ill delete it
• 03-28-2004
axon
I obviously missed something
• 03-28-2004
KneeGrow
Ahh someone please check those answers the first four are so easy just check for the roots then do e^x but i need someone to check 5 + 6

Thanks a lot
• 03-28-2004
Aran
agh.... type in sentences please :)

I only WISH i could do those problems. I guess you just aren't an english person.

[half j/k]
And, also, your cheap attempt at making it look like you have 4000 something posts is, at the very least, laughable and embarassing. Embarassing not only to you, but to all of mankind (for harboring such rabid stupidity!). :D
[/half j/k]
• 03-28-2004
KneeGrow
Okay whatever ya'll can stop posting on this thread as i have figured out all the answers Thanks to all that helped = 0 people lol? Anyways whatever