\"\"

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The expression is \"\".

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\"\"                          (Substitute x = 81)

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Square Root of a Number: If b2 = a, then b is a square root of a.

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\"\"                           (Rewrite the \"\")

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\"\"                                (The positive square root of 81 is 9)

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\"\"                                       (Subtract: \"\")\"\"

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The value of expression is \"\".