$\"\"$

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The function is $\"f$

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$\"fraction$ (Apply first derivative)

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$\"f$ (The derivative of $\"fraction$ )

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$\"f$ (The derivative of $\"left$ )

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$\"f$ (Simplify)

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$\"\"$

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$\"fraction$ (Apply second derivative)

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$\"f$ (The derivative of $\"fraction$ )

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$\"f$ (The derivative of $\"left$ )

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$\"\"$ (Simplify)

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$\"\"$

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We know $\"\"$

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$\"\"$ (Multiply each side by $\"\"$ )

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$\"\"$ (But $\"\"$ )

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$\"\"$ (Add $\"\"$ to each side)

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$\"\"$

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Therefore $\"\"$ .