$\"\"$

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Consider surfacr area of the cube is $\"\"$ , Where $\"\"$ is the edge of the cube.

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Find the rate of change in surface area $\"\"$ , when $\"\"$ .

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$\"\"$

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Apply derivative on each side with respect to $\"\"$ .

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$\"\"$

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$\"\"$

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The Power rule of derivative : $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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Substitute $\"\"$ in the above equation.

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$\"\"$

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$\"\"$ .

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Find $\"\"$ , when the edge $\"\"$ cm.

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$\"\"$

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$\"\"$

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(b).

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Find $\"\"$ , when the edge $\"\"$ cm.

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$\"\"$

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$\"\"$

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$\"\"$

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(a) $\"\"$ .

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(b) $\"\"$ .