Understanding Laplace Transform: Step 1 to 2 Difficulty

[robertjford80]

Homework Statement

The Attempt at a Solution

I can understand step 2 to 3, but I can't get step 1 to 2. For simplicity sake we'll just call e^(3-s)t = N since it will = N anyway ultimately.

I think the answer should be

[N/3-s - 1/(3-s)^2)N - (0 - 1/(3-s)^2)0

The second term is still multiplied by zero. So the answer should be infinity.

 

[Infinitum]

Your variable is t. And its limits are from 0 to N. When t=0, you have

$$e^{(3-s)t} = e^0 = 1$$

And not 0, as you got...

 

[robertjford80]

of course, how could i have forgotten.