Answer:
Step-by-step explanation:
The first derivative simplifies to ...
d/dx( ) = -(x^2 +6x -47)/(x^2 -9x +20)^2
This has zeros that can be found by the usual methods of solving quadratics:
x = -3 ±2√14
The positive value of x corresponds to what I might call an "apex." (See the first attachment.) The negative value is where the function turns around an approaches the horizontal asymptote from below. (See the second attachment.)