f(x)=x^2*e^(-|x|)
how can i solve the integral?

Question

amistre64 · Answer

i now there are some representations of e^x that cant be integrated.... forget why..

amistre64 · Answer

but for this; just int by parts using x^2 as u; and v as e^...

anonymous · Answer

Yes, but how i deal the absolute value?

amistre64 · Answer

an absolute value is always positive; and the opposite of an always positive value is always negative right?

amistre64 · Answer

just redefine it; |x| = a perhaps

anonymous · Answer

Shouldn't i divide the integral into two cases? |x| = x if x>0 and |x| = -x if x<0?

amistre64 · Answer

shadowfiend · Answer

Yeah, I think that's the way you have to go.

watchmath · Answer

Is this a definite integral or indefinite?

anonymous · Answer

The exercise is to solve the integral from -inf to inf

watchmath · Answer

That makes a difference
$\int_{-\infty}^\infty x^2e^{-|x|}=2\int_0^\infty x^2e^{-x}\,dx$
and you can use integration by parts.

amistre64 · Answer

thats what I had in mind :)  just couldnt spell it out well enough ...