PLZ HELP?!!! GUVING BRAINLIEST!! Alexandra is installing edge material around her yard. She has 400 ft of edge material to surround three sides of her rectangular yard. The fourth side will be against her deck and does not need edging. What is the maximum area that can be enclosed by the edging? Enter your answer in the box.

Answer: The answer is 20,000 feet squared.Step-by-step explanation: I don't know how ya'll got that one right but that's not how your supposed to do it. How I am currently getting taught is figuring out the length of the side parallel to the deck. That equation is 400-2xThen, you do this to solve for area;A=L*W             (substitute)A=L(400-2x)  A=x(400-2x)A=-2x^2 + 400xThen, to find the x coordinate of the parabola, you do -b/2(a)This substituted is -400 divided by -4, which equals 100.So, now we know that x=100. substitute in 100 for x, and we get;A=-2(100^2) + 400*100A=-20,000+40,000 which equals...20,000