$\"\"$

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The first derivative function is $\"\"$

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$\"\"$ .

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Apply integral on each side.

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$\"\"$

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$\"\"$ .

\

$\"\"$ .

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Apply integral on each side.

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$\"\"$

\

$\"\"$ .

\

$\"\"$

\

$\"\"$

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The function is $\"\"$

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The function $\"\"$ is continuous.

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$\"\"$ .

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$\"\"$ .

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

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$\"\"$

\

$\"\"$

\

$\"\"$ .

\

$\"\"$ .

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The function $\"\"$ is continuous at $\"\"$ .

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$\"\"$ and $\"\"$ are equal at $\"\"$ .

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$\"\"$

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$\"\"$ .

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

\

$\"\"$ .

\

The function is $\"\"$

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The $\"\"$ is differentiable at $\"\"$ . \ \

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$\"\"$

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The function is $\"\"$

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The $\"\"$ is differentiable at $\"\"$ .