# Laplace transform with time shift

1. Sep 20, 2010

### maxsthekat

1. The problem statement, all variables and given/known data

I need to find the Laplace transform of t*e-t*u(t-tau)

2. Relevant equations and attempt at solution

I know the general form of the transform, but my problem is in the time shift of the step function. If both parts of the expression were (t-tau), then I could just pull out an e(s*tau), but I have no idea what I'm supposed to do when one part has it and the other does not.

Can anyone help get me started?

2. Sep 20, 2010

### vela

Staff Emeritus
Hint:

$$te^{-t} = (t-\tau+\tau)e^{-(t-\tau+\tau)}$$