x^2 - 5x - 14
             _____________          

               4 - x^2

Rational Expressions are said to be in simplest form
when there is no common factor other than 1.
So factor both numerator and denominator.

           (x - 7) (x + 2)
           _______________

           (2 - x)(2 + x)

Divide common factor 2 + x can also be written as x + 2

             (x - 7)
             _______

             (2 - x)