# Tough integral out of strategies

1. Sep 11, 2008

### Felicity

1. The problem statement, all variables and given/known data

∫x2e-2|ax| dx

3. The attempt at a solution

tried to integrate by parts but I just ended up with a more difficult integral including an x3 times the e-2|ax|

I've also tried substituting y=2ax

to get 1/(2a)∫y2e-y dx

but where do i go from there? and can I just ignor the absolute value?

Can anybody recommend another strategy? How can I accommodate the absolute value?

Thank you

Last edited: Sep 11, 2008
2. Sep 11, 2008

### Thorn

Well, yeah...intergrate by parts!!!! and try to reduce x^2!! that is write e^(whatever) as the u'...so that when you apply the formula, you actually differentiate x^2...thus making it 2x...then do it again...and make it 2...then you will have nothing more than an integral with e(whatever that was)...You were just applying the formula wrong...and probably writing x^2 as (1/3*x^3)' ...DONT DO THAT! =)

3. Sep 11, 2008

### Thorn

OH YEAH! DONT IGNORE THE ABSOLUTE VALUE...cause e^(-x) is a lot different that e^(x)...do you have limits on that integral?

4. Sep 11, 2008

### Defennder

Just factor out a: $$|ax| = |a||x|$$. Keep the absolute sign there. Integration by parts works fine. Just do it twice.

5. Sep 11, 2008

Thank you!