Question

Tìm số tự nhiên:

a)X/5 < 4/5

b)2/17<2/x

c)1<x/7<10/7

Answer 1

a) \(\frac{x}{5}< \frac{4}{5}\)

\(\Rightarrow x< 4\)

\(\Rightarrow x=\left\{0;1;2;3\right\}\)

b) \(\frac{2}{17}< \frac{2}{x}\)

\(\Rightarrow17>x\)

\(\Rightarrow x=\left\{\frac{x\in N}{x>17}\right\}\)

c) \(1< \frac{x}{7}< \frac{10}{7}\)

\(\Leftrightarrow\frac{7}{7}< \frac{x}{7}< 10< 7\)

\(\Rightarrow7< x< 10\)

\(\Rightarrow x=\left\{8;9\right\}\)