Solution - Simplification or other simple results

Step  1  :

            1
 Simplify   —
            t

Equation at the end of step  1  :

   d              1
  (— • t) • (0 -  —)
   d              t

Step  2  :

            d
 Simplify   —
            d

Equation at the end of step  2  :

            -1
  (1 • t) • ——
            t 

Step  3  :

Final result :

  -1