Consider given the given integration,
Let,
I=∫x2tan−1x31+x6dx
Put,
t=tan−1x3
dt=11+x6.3x2dx
dx=1+x63x2
I=∫x2tan−1x31+x6dx=∫x2.t3x2dt
I=13∫tdt=13×t22+C
I=16.(tan−1x3)2+c
Hence, this is the answer.