E-OP03 · A fence with a divider and an extra restriction
A rectangular enclosure borders a straight river, so no fence is needed along the river. There is one interior divider perpendicular to the river. The total fence length, including the divider, is 60 m. Let x be the distance from the river and y the side parallel to it.
Express y and the enclosed area A in terms of x, and give the feasible interval.
Find the greatest area and the dimensions when there is no further restriction.
Now the side parallel to the river must be at least 36 m. Find the greatest area subject to this extra restriction.
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