$\"\"$

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Observe the figure :

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The perimeter of the frence is $\"\"$ is equals to $\"\"$ .

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Area of the frence is $\"\"$ .

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Consider $\"\"$ .

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Substitute $\"\"$ in $\"\"$ .

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$\"\"$

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Area of the frence is $\"\"$ .

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Substitute $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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Derivative on each side with respect to $\"\"$ .

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$\"\"$

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Equate derivative to zero.

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$\"\"$

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If $\"\"$ , then $\"\"$ .

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$\"\"$

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The dimensions are $\"\"$ and $\"\"$ . \ \