The Student Room Group

Quick Integration by Parts help C3

Please can someone explain to me step by step how to integrate: xlnx dx using integration by parts??

I had a part that I got up to when I had to integrate (xlnx - x) and I got stuck here, but not sure if my steps before this were right,
Thank you:smile:
you really want to end up differentiating the lnx part... it is much easier than integrating :colondollar:

so that means you have to integrate the other bit, which is x....
Reply 2
Original post by the bear
you really want to end up differentiating the lnx part... it is much easier than integrating :colondollar:

so that means you have to integrate the other bit, which is x....


Okay I will try and switch them round, do you know how I would integrate it in a scenario in which you had to?
Thanks :smile:
Reply 3
Original post by the bear
you really want to end up differentiating the lnx part... it is much easier than integrating :colondollar:

so that means you have to integrate the other bit, which is x....


My answer's got even worse :colondollar:
Original post by jazz_xox_
Okay I will try and switch them round, do you know how I would integrate it in a scenario in which you had to?
Thanks :smile:


you would never need to during an integration by parts.

but the answer is xlnx - x + c
Original post by jazz_xox_
My answer's got even worse :colondollar:


xlnx dx

u = lnx

du/dx = 1/x
dv/dx= x

v = x2/2

====> xlnx dx =(x2/2).lnx - x.1/x. dx

etc
(edited 6 years ago)
Reply 6
Original post by the bear
xlnx dx

u = lnx

du/dx = 1/x
dv/dx= x

v = x2/2

====> xlnx dx =(x2/2).lnx - x.1/x. dx

etc

Got it! Thank you :smile:

Quick Reply

Latest