Solution - Simplification or other simple results

Step  1  :

             d
 Simplify   ——
            dx

Canceling Out :

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

Equation at the end of step  1  :

   1           
  (— • x2) +  3x
   x           
 Step  2  :

Final result :

  4x