Calculate the inverse Laplace transform (s−2)/((s+1)^4)

Kayla Mcdowell

Kayla Mcdowell

Answered question

2022-10-24

Calculate the inverse Laplace transform s 2 ( s + 1 ) 4

Answer & Explanation

toliwask

toliwask

Beginner2022-10-25Added 15 answers

First, we should find the inverse Laplace transform of 1 ( s + 1 ) 4 . If you look at a table of Laplace transforms, you'll see that
L ( t n e a t ) = n ! ( s a ) n + 1
(this formula can be shown by induction & integration by parts). So we can see that
L ( t 3 e t 3 ! ) = 1 ( s + 1 ) 4
Most tables will also mention that
L ( f ( t ) ) ( s ) = s L ( f ( t ) ) f ( 0 )
And so we have
L ( 3 t 2 e t t 3 e t ) = L ( d d t t 3 e t ) = 3 ! s ( s + 1 ) 4
And so the inverse Laplace transform of our original function is
1 3 ! ( 3 t 2 e t t 3 e t 2 t 3 e t )
Payton George

Payton George

Beginner2022-10-26Added 1 answers

Note that s 2 ( s + 1 ) 4 = 1 ( s + 1 ) 3 3 ( s + 1 ) 4
With σ , μ > 0 _
f ( μ ) σ i σ + i e s t s + μ d s 2 π i = e μ t
{ σ i σ + i e s t ( s + 1 ) 3 d s 2 π i = 1 2 f ( 1 ) = 1 2 t 2 e t σ i σ + i e s t ( s + 1 ) 4 d s 2 π i = 1 6 f ( 1 ) = 1 6 t 3 e t
S o l u t i o n : 1 2 t 2 e t 3 ( 1 6 t 3 e t ) = 1 2 t 2 ( 1 t ) e t

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