The given integral =−0∫−1ln(1+x+x2)x(1+x)dx
=0∫−1ln(1+x+x2)1+xdx−0∫−1ln(1+x+x2)xdx
=0∫−1ln[1+(−1−x)+(−1−x)2]1+(−1−x)dx−0∫−1ln(1+x+x2)xdx
=0∫−1ln(1+x+x2)−xdx−0∫−1ln(1+x+x2)xdx
=−20∫−1ln(1+x+x2)xdx
=−20∫−1ln(1−x)(1+x+x2)(1−x)xdx
=20∫−1ln(1−x)(1−x3)xdx
=20∫−1ln(1−x)xdx−20∫−1ln(1−x3)xdx ......(*)
Consider, I=0∫−1ln(1−x3)xdx
Let, x3=t
⇒3x2dx=dt
⇒dxx=dt3x3=dt3t
So, I=0∫−1ln(1−t)3tdt
I can also be written as 0∫−1ln(1−x)3xdx
From (*), the given integral
=20∫−1ln(1−x)xdx−20∫−1ln(1−x)3xdx
=430∫−1ln(1−x)xdx
=430∫−1−x−x22−x33−x44−........xdx
=−430∫−11+x2+x23+x34+.........dx
=−43(x+x222+x332+x442+..........)|0−1
=−43[0−(1+122+132+142+.........)]
=43(1+122+132+142+.........)