$\"\"$

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The equation is $\"\"$ .

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Solve the above equation for $\"\"$ .

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$\"\"$

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Square on both sides.

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$\"\"$

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$\"\"$

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Divide each side by $\"\"$ .

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$\"\"$

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$\"\"$ .

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$\"\"$

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For any input of $\"\"$ , we get only one output for $\"\"$ .

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An input $\"\"$ .

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

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$\"\"$

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$\"\"$ .

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An input $\"\"$ .

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

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$\"\"$

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$\"\"$

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For any input of $\"\"$ , we get only one output for $\"\"$ .

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So, the equation $\"\"$ defines $\"\"$ as a function of $\"\"$ .

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$\"\"$

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The equation $\"\"$ is a function.