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Question Number 75873 by Rio Michael last updated on 19/Dec/19

∫xe^x dx

xexdx

Answered by MJS last updated on 19/Dec/19

u′=e^x  ⇒ u=e^x   v=x ⇒ v′=1  ∫u′v=uv−∫uv′  ∫xe^x dx=xe^x −∫e^x dx=xe^x −e^x =  =(x−1)e^x +C

u=exu=exv=xv=1uv=uvuvxexdx=xexexdx=xexex==(x1)ex+C

Commented by Rio Michael last updated on 21/Dec/19

excuse me sir am kinda confused  when it comes to these by parts stuffs  why can′t we  take  u′ = x ⇒ u = (1/2)x^2

excusemesiramkindaconfusedwhenitcomestothesebypartsstuffswhycantwetakeu=xu=12x2

Commented by MJS last updated on 21/Dec/19

try it  u′=x ⇒ u=(1/2)x^2   v=e^x  ⇒ v′=e^x   ∫u′v=uv−∫uv′  ∫xe^x dx=(1/2)x^2 e^x −(1/2)∫x^2 e^x dx  the point is, we must try to find u, v to make  it easier

tryitu=xu=12x2v=exv=exuv=uvuvxexdx=12x2ex12x2exdxthepointis,wemusttrytofindu,vtomakeiteasier

Commented by Rio Michael last updated on 21/Dec/19

okay,so we just choose to make our problem easier.

okay,sowejustchoosetomakeourproblemeasier.

Commented by MJS last updated on 21/Dec/19

yes. but it can be tricky sometimes

yes.butitcanbetrickysometimes

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