If y=tan−1(11+x+x2)+tan−1(1x2+3x+3)+tan−1(1x2+5x+7)+⋯⋯⋯ n terms, then y'(0) is
π/2
tan−1(11+x+x2)=tan−1(x+1−x1+x+(x+1))=tan−1(x−1)−tan−1x similarly other terms
If y=tan−1(11+x+x2)+tan−1(1x2+3x+3)+tan−1(17+5x+x2)+…n terms, then (dydx)x=0=