I am having an interesting time with my friend, Don Quixote, on our adventures. He is a bit silly, as he believes he is a knight on a quest. Just yesterday he attacked a windmill because he thought it was a giant. [ I had better stay with him though - he might get into some serious trouble if he doesn't have someone to watch out for him. I don't know when I will be able to return home. Your friend, Sancho. ]
P = 2x+2(450-x)=900 A = x(450 - x) A = x(450 - x) -x² + 450x = A -x² +450x = A A is going to be maximum, when x is a vertex. -(x² - 450x) = A -(x² - 2*225x+225²) - 225² =A -(x-225)² -225² = A Vertex when x=225