Question

[kiên phan]

s= 1/11+1/12+1/13+...+1/20 chứng minh s<5/6

Answer 1

[kiên phan]

nhanh giúp mik vs

Answer 2

[T.Ps]

#)Giải :

Ta có : \(\frac{1}{11}+\frac{1}{12}+\frac{1}{13}+...+\frac{1}{20}>\frac{1}{20}+\frac{1}{20}+\frac{1}{20}+...+\frac{1}{20}=\frac{10}{20}=\frac{1}{2}< \frac{5}{6}\)(có 10 số \(\frac{1}{20}\))

\(\Rightarrow\frac{1}{11}+\frac{1}{12}+\frac{1}{13}+...+\frac{1}{20}< \frac{5}{6}\)

Hay \(S< \frac{5}{6}\left(đpcm\right)\)