Question

Các bn giúp mình làm bài 9 nhé

Answer 1

Ta có:

\(\dfrac{1}{51}>\dfrac{1}{100},\dfrac{1}{52}>\dfrac{1}{100},...,\dfrac{1}{100}=\dfrac{1}{100}\)

\(\Rightarrow\dfrac{1}{51}+\dfrac{1}{52}+...+\dfrac{1}{100}>\dfrac{1}{100}.50=\dfrac{1}{2}\left(1\right)\)

\(\dfrac{1}{51}< \dfrac{1}{50},\dfrac{1}{52}< \dfrac{1}{50},...,\dfrac{1}{100}< \dfrac{1}{50}\)

\(\Rightarrow\dfrac{1}{51}+\dfrac{1}{52}+...+\dfrac{1}{100}< \dfrac{1}{50}.50=1\left(2\right)\)

Từ (1),(2)\(\RightarrowĐPCM\)