Question

so sánh: 

1/31+1/32+...+1/39+1/40 và 1/4

Answer 1

Ta có :

\(\frac{1}{31}>\frac{1}{40};\frac{1}{32}>\frac{1}{40};...;\frac{1}{40}=\frac{1}{40}\)

\(\frac{1}{31}+\frac{1}{32}+...+\frac{1}{39}+\frac{1}{40}\)

\(>\frac{1}{40}+\frac{1}{40}+...+\frac{1}{40}+\frac{1}{40}=\frac{1}{40}.10=\frac{1}{4}\)

Answer 2

\(\frac{1}{31}+\frac{1}{32}+..................+\frac{1}{39}+\frac{1}{40}>\frac{1}{4}\)

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