Can't seem to get this DE solved using laplace transforms

1MileCrash
Messages
1,338
Reaction score
41

Homework Statement



y''-4y'+4y = 0
y(0)=1, y'(0)=1

Homework Equations





The Attempt at a Solution



This is annoying, because it feels very easy and I don't know why I am not getting the answer. Skipping the routine:

s^2L{y} - s - 1 - 4sL{y} + 4 + 4L{y} = 0

(s+3) / (s^2 - 4s + 4) = L{y}

= s/(s-2)^2 + 3/(s-2)^2

= 1/(s-2) + 2(1/(s-2)^2) +3(1/(s-2)^2)

= 5(1/(s-2)^2) + 1/(s-2)


The inverse transform of which gives:

5te^2t + e^2t = (5t+1)e^2t


Any ideas?

Thanks!
 
NVM, I think it should be s-3 in num now.
 
Check your signs.

EDIT: Ah, I see you found the mistake.
 

Similar threads

  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 10 ·
Replies
10
Views
3K
Replies
2
Views
2K
  • · Replies 8 ·
Replies
8
Views
2K
Replies
9
Views
3K
  • · Replies 4 ·
Replies
4
Views
3K
  • · Replies 1 ·
Replies
1
Views
1K
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
Replies
4
Views
2K