# Integration and taylor expansion

can anybody help me with this integration?

Integral of e to the -2x times x squared dx

it expands to 1/4, but I'm not sure how to start.

Hootenanny
Staff Emeritus
Gold Member
can anybody help me with this integration?

Integral of e to the -2x times x squared dx

it expands to 1/4, but I'm not sure how to start.
Hey casanova, welcome to PF!

You don't really need a Taylor expansion here, how about trying a substitution?

I have tried substitution

argh!

i've tried u = e ^ -2x

I've also tried u = x squared.

it doesn't work!!!!

HELP!

Integrate by parts and it works.

start me off

with what do I start?

rock.freak667
Homework Helper
with what do I start?

you start by integrating

$$\int xe^{-2x}dx$$

by parts.

u = x^2
du = 2x dx

dv = e^-2x dx
v = -1/2 e^-2x

Give it a shot from there.

thanks

i get it now....just needed a refresher....thanks a lot!