, and
. Subtract this from the numerator and you get a remainder of
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, and
. Subtract this from the previous remainder and you get a new remainder of
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, and
. Subtract this from the previous remainder and you get a new one of
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, and
. Subtract this from the previous remainder and you get a new one of
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doesn't divide 120, so we're done, and putting everything together we've shown that
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