$\"\"$

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The function is $\"\"$ and the point is $\"\"$ .

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Apply partial derivative on each side with respect to x .

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$\"\"$

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$\"\"$

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Substitute the point $\"\"$ in above function.

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$\"\"$

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$\"\"$ .

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$\"\"$

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The function is $\"\"$ .

\

Apply partial derivative on each side with respect to y.

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$\"\"$

\

$\"\"$

\

Substitute the point $\"\"$ in above function.

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$\"\"$

\

$\"\"$ .

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$\"\"$

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$\"\"$ .

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$\"\"$ .