$\"\"$

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The equation is $\"\"$ .

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Take natural logarithm on each side.

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$\"\"$

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Product property of logarithm : $\"\"$ .

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$\"\"$

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Power property of logarithm : $\"\"$ .

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$\"\"$

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Differentiate with respect to $\"\"$ .

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$\"\"$

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$\"\"$

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$\"\"$

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$\"\"$ .