$\"\"$ \ \

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

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The equation of the tangent plane to the surface $\"\"$ at a point $\"\"$ is \ \

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$\"\"$ \ \

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Consider $\"\"$

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Differentiate on each side with respect to $\"\"$ , holding $\"\"$ as a constant. \ \

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$\"\"$

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$\"\"$ .

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Differentiate on each side with respect to $\"\"$ , holding $\"\"$ as a constant.

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$\"\"$

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$\"\"$ \ \

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Find the equation of the tangent plane. \ \

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The equation of the tangent plane at a point $\"\"$ is \ \

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$\"\"$ \ \

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$\"\"$ \ \

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$\"\"$ \ \

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The equation of the tangent plane is $\"\"$ . \ \