Question 772394
You are really asking for {{{(d/dx) ((-1)/(1+x^2))}}}


= {{{(d/dx)(-1(1+x^2)^-1)=(-1)(-1)((1+x^2)^-2)(d/dx)(1+x^2)}}}
= {{{(1/(1+x^2)^2)*2x}}}
{{{(2x)/(1+x^2)^2}}}