______y__________y______

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A person has 400 ft. of fencing to maximize the area. What are the dimensions?

400=4y + 3x

A=2xy

57.143=y+x

y=57.143-x

A=2(57.143-x)(x)

A=114.286x-2x^2

A'=114.286-4x=0

114.286=4x

x=28.572

400=4y+3(28.572)

400=4y+85.715

315.286=4y

y=78.571

x=28.572 ft.

y=78.571 ft.

Does this look right?