# Math Help - where is my mitake here ,i shouldnt get 0

1. ## where is my mitake here ,i shouldnt get 0

[tex]
\int_{0}^{x}e^{-t}tdt=1e^{-t}-\int_{0}^{x}-e^{-t}=0
[/MATH $]v'=e^{-t}$ u=t
$v=-e^{-t}$ u'=1

2. Originally Posted by transgalactic

$\displaystyle \int_{0}^{x}e^{-t}tdt=1e^{-t}-\int_{0}^{x}-e^{-t}dt=0$

$v'=e^{-t}$

u=t

$v=-e^{-t}$

u'=1
When applying integration by parts

$\int{u}dv=uv-\int{v}du$

you did not multiply $uv$ correctly. You forgot $u=t$

and got the sign wrong on $v$