Laplace Transform

• Apr 14th 2009, 05:12 PM
leebatt
Laplace Transform
How do you find the Laplace transform of t(u[t+4])? I know what to do if it is u(t-4).

Thank you for your time
• Apr 14th 2009, 07:35 PM
mr fantastic
Quote:

Originally Posted by leebatt
How do you find the Laplace transform of t(u[t+4])? I know what to do if it is u(t-4).

Thank you for your time

$LT \left[t^n f(t) \right] = (-1)^n \frac{d^n F(s)}{ds^n}$ where $F(s) = LT[f(t)]$.

In particular $LT \left[t f(t) \right] = - \frac{d F(s)}{ds}$.