Integration problem

  • Thread starter semc
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  • #1
356
3
[tex]\int\frac{x}{x^4+x^2+1}[/tex]dx

Okay the question ask to integrate the above expression so the first thing i did was to equate u=x2 so u'=2x and got this [tex]\frac{1}{2}[/tex][tex]\int\frac{1}{u^2+u+1}[/tex]du. I then proceed to use integration by parts which i find that this method is too long and messy so i was wondering is there a better to do this :smile:
 

Answers and Replies

  • #2
Perfectly well done. But now, convert the ^2 + u + 1 into a friendlier term -->

(u + 0.5)^2 + 0.75

Now, integrate this, it's a direct formula based problem --> will go into tan inverse.
 
  • #3
356
3
Damn why didn't i thought of that haha i get it now thanks mate~
 
  • #4
If you are solving integrals for the first time, it's really okay.

Try solving the problem with x2 in the numerator instead of x. This one is not a simple one, and has a whole lot of pages in the miscellaneous section devoted to it.
 
  • #5
356
3
I just notice something, if we are using the anti derivative, shouldn't the denominator be 1+x2? In this case its 0.75 so how do we do it?
 
  • #6
Bracket out the 0.75^2 from the denominator and take it outside the integral. Now you have something sqared plus 1 in the denominator. Now, sbstitte that something = v and integrate. Then resubstitute everything, back again.
 

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