\"\"

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The side lengths of a right triangle are \"\" ; \"\"

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Apply Pythagorean theorem: \"a

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\"\"                        (Substitute 9 for a and 15 for c)

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\"\"                      (Evaluate powers: \"\")\"\"

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\"\"      (Subtract 81 from each side)

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

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\"\"                       (Take square root to each side)

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\"\"                        (Write \"\")

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\"\"                                  (Cancel square and root)\"\"

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The unknown length of \"\".