# Laplace transform using properties

1. Dec 20, 2011

### phlstr

1. The problem statement, all variables and given/known data
Find the laplace transform of
f(t)=(t-5)e$^{-17(t-5)}$u(t-5)

3. The attempt at a solution

The answer I got was $\frac{e$^{-5(s+17)}$}{(s+17)^{2}}$.
I thought I finally understood the process, but when I plugged it into wolfram alpha, the answer I got was different...

http://www.wolframalpha.com/input/?i=laplace+transform+of+((t-5)e^(-17(t-5)))*theta(t-5)

Shouldn't the "s" in the exponent be "s+17" or is my understanding really wrong??

2. Dec 20, 2011

### vela

Staff Emeritus
Wolfram Alpha's answer is the correct one.