Let
I=∫02x+1x4+x2+1x(x2+x+1)dx.
Using the identity
x4+x2+1=(x2+x+1)(x2−x+1):
I=∫02x+1(x2+x+1)(x2−x+1)xx2+x+1dxCancelling
x2+x+1:
I=∫02(x+1)(x2−x+1)xdxUsing
(x+1)(x2−x+1)=x3+1:
I=∫02x3+1xdxSubstitution:
Let
t=x3/2, so
dt=23x1/2dx⇒xdx=32dt.
Also,
t2=x3, so
x3+1=t2+1.
Changing limits:
x=0⇒t=0x=2⇒t=23/2=22Therefore:
I=32∫022t2+1dtUsing
∫t2+a2dt=loget+t2+a2+C:
I=32[loge(t+t2+1)]022I=32[loge(22+8+1)−loge(1)]I=32loge(22+3)I=32loge(3+22)Hence, the correct option is
(3) 32loge(3+22).