$\"\"$

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The equation of a tangent plane : $\"\"$ . $\"\"$

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

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Rewrite the equation as $\"\"$ .

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Consider $\"\"$ .

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Differentiate $\"\"$ partially with respect to $\"\"$ .

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$\"\"$

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

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$\"\"$ .

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Differentiate $\"\"$ partially with respect to $\"\"$ .

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$\"\"$

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

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$\"\"$ .

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Differentiate $\"\"$ partially with respect to $\"\"$ .

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$\"\"$

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

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$\"\"$ . $\"\"$

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The equation of the tangent plane is $\"\"$ Substitute $\"\"$ , $\"\"$ and $\"\"$ in above equation. $\"\"$

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

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The symmetric equations are $\"\"$ . $\"\"$

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

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The symmetric equations are $\"\"$ .