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#1
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͹ءÃÁ 1+1/2+...+1/20
¨§ËÒ $1+\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{20}$ ¢Íá¹Ç¤Ô´¤ÃѺ
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#2
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äÁèÁÕá¹Ç¤Ô´¤ÃѺ
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#3
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ÍéÒ§ÍÔ§:
$$1+\int_2^{21}\frac{1}{x} dx < 1 + \frac{1}{2} + ... + \frac{1}{20} < 1 + \int_1^{20}\frac{1}{x}dx$$ $$1+ \ln 21 - \ln 2 < 1+ ... + \frac{1}{20} < 1 + \ln 20$$ |
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