It is proved that the function y = x-ln (1 + x ^ 2) increases monotonically

It is proved that the function y = x-ln (1 + x ^ 2) increases monotonically


Do it by derivation
y'=1-(2x)/(1+x^2)=(1+x^2-2x)/(1+x^2)=(x-1)^2/(x^2+1)>=0
So the function is an increasing function