Question

Số các số tự nhiên n thỏa mãn \(\dfrac{2}{1}< \dfrac{1}{n}< \dfrac{4}{7}\) là ...

Answer 1

Ta có: \(\dfrac{2}{1}< \dfrac{1}{n}< \dfrac{4}{7}\)

\(\Rightarrow\dfrac{4}{2}< \dfrac{4}{4n}< \dfrac{4}{7}\)

\(\Rightarrow2< 4n< 7\)

\(\Rightarrow0,5< n< 1,75\)

Mà \(n\in N\)

\(\Rightarrow n=1\)

Vậy n = 1

Answer 2

\(\dfrac{2}{1}< \dfrac{1}{n}< \dfrac{4}{7}\)

\(\Rightarrow\dfrac{4}{2}< \dfrac{4}{4n}< \dfrac{4}{7}\)

\(\Rightarrow2< 4n< 7\)

\(\Rightarrow\dfrac{2}{4}< \dfrac{n}{4}< \dfrac{7}{4}\)

\(\Rightarrow0,5< n< 1,75\)

\(n\in N\Rightarrow n=1\)