# Thread: different int. by parts

1. ## different int. by parts

$\int \frac{2x}{e^x}dx$

I tried:
u=2x
dv= $e^{-x}dx$

but I got a funky answer. Is this the correct substitution?

Still learning which to use when...lol

2. Originally Posted by saiyanmx89
$\int \frac{2x}{e^x}dx$

I tried:
u=2x
dv= $e^{-x}dx$

but I got a funky answer. Is this the correct substitution?

Still learning which to use when...lol

Yes.

3. Originally Posted by saiyanmx89
$\int \frac{2x}{e^x}dx$

I tried:
u=2x
dv= $e^{-x}dx$

but I got a funky answer. Is this the correct substitution?

Still learning which to use when...lol
$\int \frac{2x}{e^x}dx = \int 2xe^{-x}dx$

$= 2 \bigg(\bigg[ -xe^{-x}\bigg] - \int -e^{-x} dx \bigg)$