First, factor the denominator.
x3+x2−x−1=x2(x+1)−(x+1)=(x2−1)(x+1)=(x−1)(x+1)(x+1)=(x−1)(x+1)2. Then we can rewrite the integral as:
J=∫(x−1)(x+1)26x2+4xdx. We can use partial fraction decomposition to split the fraction into simpler terms:
(x−1)(x+1)26x2+4x=x−1A+x+1B+(x+1)2C 6x2+4x=A(x+1)2+B(x−1)(x+1)+C(x−1) 6x2+4x=A(x2+2x+1)+B(x2−1)+C(x−1) 6x2+4x=Ax2+2Ax+A+Bx2−B+Cx−C 6x2+4x=(A+B)x2+(2A+C)x+(A−B−C) Comparing coefficients:
From the first equation, we have B=6−A. From the third equation, we have C=A−B=A−(6−A)=2A−6. Substituting C into the second equation: 2A+2A−6=4 A=410=25. B=6−25=212−25=27. C=2(25)−6=5−6=−1. Thus, we have
(x−1)(x+1)26x2+4x=x−15/2+x+17/2+(x+1)2−1. Now we can rewrite the integral:
J=∫(x−15/2+x+17/2−(x+1)21)dx J=25∫x−11dx+27∫x+11dx−∫(x+1)21dx J=25ln∣x−1∣+27ln∣x+1∣+x+11+C