Savol 1

$arctg\left(x\right)·x-\ln \left|x^2-1\right|+C$

$arctg\left(x\right)·x+\frac{1}{2}·\ln \left|1+x^2\right|+C$

$arctg\left(x\right)·x-\frac{1}{2}·\ln \left|1+x^2\right|+C$

$arctg\left(x\right)-\frac{1}{2}·\ln \left|1+x^2\right|+C$