



 
Hi Shirlyn, Here is my diagram. AB = 60 ft, BC = 80 ft, FB = y ft, BG = x ft and EF = a ft. Since triangles ABC and FBG are similar 60/80 = y/x and hence y = 3/4 x. AF = 60  y ft and Pythagoras theorem tells us that FG = √(x^{2} + y^{2}) ft. Triangles AFE and FBG are similar which allows you to find an expression for a × √(x^{2} + y^{2}) in terms of x and y. But a × √(x^{2} + y^{2}) is the area of the rectangle EFGD and now you can use the fact that y = 3/4 x to write the area of the rectangle in terms of x alone. Your knowledge of calculus now allows you to complete the problem. Penny  


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