Please explain me, I don't understand how they got it. http://www.wolframalpha.com/input/?i=int+%284x^%28-3%29lnx+dx%29

Question

loser66 · Answer

if taking integral by part, let g = lnx $\rightarrow$ dg =1/x dx and df = x^(-3) dx and don't understand next line

loser66 · Answer

woa!! today I am lucky. It's not easy to get your help @satellite73

anonymous · Answer

it is parts right?

loser66 · Answer

I don't know how they get the last 2 lines

anonymous · Answer

what lines? oh hold on let me look

anonymous · Answer

lets just do it

loser66 · Answer

I did, not as they did

anonymous · Answer

$$\int udv=uv-\int vdu$$ pick $$u=\ln(x), du =\frac{dx}{x}, dv=\frac{1}{x^3},v=-\frac{1}{2x^2}$$

loser66 · Answer

yes, so, uv = -$\dfrac{lnx}{2x^2}$

loser66 · Answer

and vdu = $\int \dfrac{1}{x^3}$dx

loser66 · Answer

they get $uv = \dfrac{2lnx}{x^2}$

anonymous · Answer

i better write this down, give me a sec

loser66 · Answer

@satellite73  I got it, heehe, sorry friend, because of 4 in the front., they got that answer

anonymous · Answer

oh you got a 4 in front

anonymous · Answer

lol what you said!!

loser66 · Answer

XD

anonymous · Answer

guess i dropped the 4 somewhere too, maybe in what i wrote above
that is a load of my mind

loser66 · Answer

Thanks a lot.

anonymous · Answer

i didn't do much, but you're welcome