I have this problem ∫−5x+11(x+1)(x2+1)dx
And i'm not sure how to deal with this. I've tried substitution and getting nowhere. I've peeked at the answer and there a trigonometric part with arctan. Do i use Partial fraction expansion here?
Thanks
Answer
use the partial fraction to get
−5x+11(x+1)(x2+1)=3−8xx2+1+8x+1=3x2+1−8xx2+1+8x+1
details:
−5x+11(x+1)(x2+1)=Ax+Bx2+1+C1+x=(Ax+B)(1+x)+C(x2+1)(x2+1)(1+x)
−5x+11(x+1)(x2+1)=Ax+Ax2+B+Bx+Cx2+C(x2+1)(1+x)
A+B=−5
A+C=0
B+C=11
solve these simultaneous equations to get
A=−8
B=3
C=8
so the integral will be
∫(3x2+1−8xx2+1+8x+1)dx=3tan−1x−4log(x2+1)+8log(x+1)+C
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