What is the correct reason for (z) that will show proof.

Ineed i been stuck on this question since yesterday

Triangle knm is what is true about the sides of knm

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