If ∫b0dx1+x2=∫∞bdx1+x2,then b=
tan−1(13)
√32
√2
1
tan−1b=tan−1∞−tan−1b
2tan−1b=π2⇒b=1
If ddx[1+x2+x41+x+x2]=ax+b then(a,b)=