Derivative of u(t)*t*e^(-5t) using product rule

[mr_coffee]

Hello eveyrone, I think my brain just shut down, I'm confused on how i would take the derivative of this function i have circled below:
http://img100.imageshack.us/img100/1671/lastscan2vi.jpg

I know the chain rule, like if it was
t*e^(-5t) = e^(-5t) + t*(-5)e^(-5t)

 

[gulsen]

$$(u_2 t e^{-7t})' = u_2' t e^{-7t} + u_2 (e^{-7t} + t (-7)e^{-7t})$$

 

[mr_coffee]

Ahh thank u! I c it now!