Question 916206
If x side of a rectangular field is to have a sea as boundary, find the dimensions of the largest rectangular field that can be enclosed by using 240 m of fencing material for the other three sides?
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let y=width of rectangle
let x=length (side facing the sea)
x=240-2y
Area=y*x=y*(240-2y)=240y-2y^2
=-2y^2+240y
complete the square:
=-2(y^2-120y+3600)+7200
=-2(y-60)^2+7200
dimensions:
y=60 m (width)
x=240-2y=240-120=120 m(length)