$\"\"$

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The equation is $\"\"$ .

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

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$\"\"$ .

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Product rule of derivatives : $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$ .

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$\"\"$

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(a)

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Find $\"\"$ when $\"\"$ and $\"\"$ .

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The equation is $\"\"$ .

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Substitute $\"\"$ in the equation.

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$\"\"$

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Substitute $\"\"$ , $\"\"$ and $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$ .

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$\"\"$

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(b)

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Find $\"\"$ when $\"\"$ and $\"\"$ .

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The equation is $\"\"$ .

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Substitute $\"\"$ in the equation.

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$\"\"$

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Substitute $\"\"$ , $\"\"$ and $\"\"$ in $\"\"$ .

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$\"\"$

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$\"\"$ .

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$\"\"$

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(a) $\"\"$ .

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(b) $\"\"$ .