Let,
I=∫2(x2+1)2dx
I=2∫1(x2+1)2dx
Applying reduction formula, we have
∫1(ax2+b)ndx=2n−32b(n−1)∫1(ax2+b)n−1dx+x2b(n−1)(ax2+b)n−1
Therefore,
I=x(x2+1)+∫1x2+1dx+C
I=x(x2+1)+tan−1x+C
∫x2x4−x2−12dx