Quick laplace transform question

In summary, the conversation is about the Laplace Transform of different expressions. The person is asking why 2/((s+4)^2) is equal to 2xe^-4x, and if they need to add an x if the numerator is a constant other than 1. The other person suggests evaluating the Laplace Transform of the expression to see what they get. The first person reports back that they got 2*e^(-4*x), but they don't understand where the extra x came from. The other person suggests doing the integration and asks why the leading x was not included. The conversation then shifts to discussing the original statements made and how it is important to say what you mean.
  • #1
orangeincup
123
0

Homework Statement


So I know 1/(s-a)=e^(a1), but why is say, 2/((s+4)^2) equal to 2xe^-4x? Do I just simply add an X if the numeration is a constant other than 1?
 
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  • #2
Why don't you evaluate the Laplace transform of the expression and see what you get?
 
  • #3
2*e^(-4*x) is what I get, I don't know where the other x came from.

Well I mean I know it's because it's squared, I just don't see how my laplace transform formula is giving me that
 
  • #4
orangeincup said:
2*e^(-4*x) is what I get, I don't know where the other x came from.

Well I mean I know it's because it's squared, I just don't see how my laplace transform formula is giving me that
Like I said, evaluate the LT of the expression with the x's and report back with what you got.
 
  • #5
L(2x*e^(-4x)) = 2x* 1/(s-4)
 
  • #6
Am I suppose to treat it as two different Laplace transforms combined? Not sure how that would work but I know the two individual formulas below
2/((s+4)^2)

1/s^n = t^n-1/(n-1)! = x*2
and
1/(s-a) = e^-4x
 
  • #7
orangeincup said:
L(2x*e^(-4x)) = 2x* 1/(s-4)
Let's see you do the integration. How come you didn't include the leading x in the integration?

Chet
 
  • #8
By the way, your original statements, that "1/(s-a)=e^(at)" and that "2/((s+4)^2) is equal to 2xe^-4x" are non-sense. You knew that when you wrote them, didn't you? What you meant was that "1/(s- a)" is the Laplace Transform" of "e^(at)" and that "2/((s+ 4)^2)" is the Laplace Transform of "2xe^(-x)". It is always better to say what you mean!
 

1. What is a Laplace transform?

A Laplace transform is a mathematical tool used to convert a function of time into a function of complex frequency. It is commonly used in engineering and physics to analyze systems and solve differential equations.

2. What is the purpose of using a Laplace transform?

The purpose of using a Laplace transform is to simplify the analysis of a system by converting it into a different domain. This can make it easier to solve differential equations and understand the behavior of a system.

3. How do you perform a Laplace transform?

To perform a Laplace transform, you can use a table of Laplace transforms or the definition of the transform, which involves integration. The transformed function will be a function of complex frequency, denoted as F(s).

4. What is the inverse Laplace transform?

The inverse Laplace transform is the process of converting a function of complex frequency back into a function of time. It is denoted as f(t) and can be found using a table of inverse Laplace transforms or by using the inverse Laplace transform formula.

5. What are the applications of Laplace transforms?

Laplace transforms have many applications in engineering and physics, such as in circuit analysis, control systems, signal processing, and heat transfer. They are also used in solving differential equations and in Fourier analysis.

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