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# Quick Integration by Parts help C3 watch

1. 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
2. you really want to end up differentiating the lnx part... it is much easier than integrating

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

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
4. (Original post by the bear)
you really want to end up differentiating the lnx part... it is much easier than integrating

so that means you have to integrate the other bit, which is x....
5. (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
you would never need to during an integration by parts.

but the answer is xlnx - x + c
6. (Original post by jazz_xox_)
∫ xlnx dx

u = lnx

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

v = x2/2

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

etc
7. (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

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