Integration and taylor expansion

  • #1

Main Question or Discussion Point

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.
 

Answers and Replies

  • #2
Hootenanny
Staff Emeritus
Science Advisor
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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?
 
  • #3
I have tried substitution

I've already tried substitution.

argh!

i've tried u = e ^ -2x

I've also tried u = x squared.

it doesn't work!!!!

HELP!
 
  • #4
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Integrate by parts and it works.
 
  • #5
start me off

with what do I start?
 
  • #6
rock.freak667
Homework Helper
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with what do I start?
you start by integrating

[tex]\int xe^{-2x}dx[/tex]

by parts.
 
  • #7
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You integrate by parts. Start with x squared. You get

u = x^2
du = 2x dx

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

Give it a shot from there.
 
  • #8
thanks

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

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