# Math Help - Laplace Transform

1. ## 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

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