Math question triangles ade and triangles abc or similar which best explains why the slope of the line between. a and d is the same as the slope between point a and b give me the answer

Marquise has 200 meters of fencing to build a rectangular garden. the garden's area (in square meters) as a function of the garden's width w w (in meters) is modeled by: a ( w ) = − w 2 + 1 0 0 w a(w)=−w 2 +100w what side width will produce the maximum garden area? meters