How to find inverse laplace of ((s^2−6s+7))/((s^2−4s+5)^2)?

Krish Crosby

Krish Crosby

Answered question

2022-09-22

How to find inverse laplace of ( s 2 6 s + 7 ) ( s 2 4 s + 5 ) 2 ?
i tried partial frictions but i get 2 2 s ( s 2 4 s + 5 ) 2 + 1 s 2 4 s + 5

Answer & Explanation

berzamauw

berzamauw

Beginner2022-09-23Added 9 answers

Just another way:
L s 1 [ s 2 6 s + 7 ( s 2 4 s + 5 ) 2 ] ( t ) = t ( L s 1 [ s 2 6 s + 7 ( s 2 4 s + 5 ) 2 d s ] ( t ) ) = t ( L s 1 [ 3 s 5 4 s + s 2 ] ( t ) )
Using Heaviside's expansion formula for: L s 1 [ 3 s 5 4 s + s 2 ] ( t ) we have:
P ( s ) = 3 s
Q ( s ) = 5 4 s + s 2
Q ( s ) = 4 + 2 s
solve roots for:Q(s)
α 1 = 2 i and α 2 = 2 i
P ( α 1 ) exp ( t α 1 ) Q ( α 1 ) + P ( α 2 ) exp ( t α 2 ) Q ( α 2 ) = P ( 2 i ) exp ( t ( 2 i ) ) Q ( 2 i ) + P ( 2 + i ) exp ( t ( 2 + i ) ) Q ( 2 + i ) = ( 1 2 + i 2 ) exp ( t ( 2 i ) ) + ( 1 2 i 2 ) exp ( t ( 2 + i ) ) = e 2 t ( cos ( t ) + sin ( t ) )
and then:
t ( L s 1 [ 3 s 5 4 s + s 2 ] ( t ) ) = t e 2 t ( cos ( t ) + sin ( t ) ) = e 2 t t ( cos ( t ) sin ( t ) )

Do you have a similar question?

Recalculate according to your conditions!

New Questions in Differential Equations

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?