Chứng minh: \(\dfrac{1}{9}+\dfrac{1}{10}+\dfrac{1}{11}+\dots+\dfrac{1}{128}>2\)
Chứng minh: \(\dfrac{1}{2}+\dfrac{1}{3}+\dfrac{1}{4}+\dots+\dfrac{1}{15}< 3\)
Chứng minh rằng: \(\dfrac{1}{201}+\dfrac{1}{202}+\dfrac{1}{203}+\dots+\dfrac{1}{400}< \dfrac{5}{6}\)
Chứng minh rằng: \(\dfrac{1}{11}+\dfrac{1}{12}+\dfrac{1}{13}+\dots+\dfrac{1}{20}< 1\)
\(\dfrac{1}{5+1}\)+\(\dfrac{2}{5^2+1}\)+\(\dfrac{3}{5^3+1}\)+....+\(\dfrac{202}{5^{202}+1}\) < \(\dfrac{1}{4}\)
Chứng minh giúp em ạ!!!
\(\dfrac{1}{5+1}\)
\(S=\dfrac{1}{31}+\dfrac{1}{32}+...+\dfrac{1}{60}\) Chứng minh \(\dfrac{3}{5}< S< \dfrac{4}{5}\)
Bài 7:
Chứng minh rằng: \(\dfrac{3}{10}< \dfrac{1}{3^2}+\dfrac{1}{4^2}+\dfrac{1}{5^2}+...+\dfrac{1}{100^2}< \dfrac{1}{2}.\)
b, Cho tổng : \(\dfrac{1}{31}+\dfrac{1}{32}+...+\dfrac{1}{60}\) Chứng minh \(\dfrac{3}{5}< S< \dfrac{4}{5}\)
b, Cho tổng : \(\dfrac{1}{31}+\dfrac{1}{32}+...+\dfrac{1}{60}\) .Chứng minh: \(\dfrac{3}{5}< S< \dfrac{4}{5}\)