Solution - Simplification or other simple results

Step  1  :

               x   
 Simplify   ———————
            y2 + x2

Equation at the end of step  1  :

   d      x   
  —— • ———————
  dy   y2 + x2

Step  2  :

             d
 Simplify   ——
            dy

Canceling Out :

 2.1    Canceling out d as it appears on both sides of the fraction line

Equation at the end of step  2  :

  1      x   
  — • ———————
  y   y2 + x2

Step  3  :

Final result :

        x      
  —————————————
  y • (y2 + x2)