Question

Tìm x: 

\(\dfrac{-4}{15}< \dfrac{5x-1}{18}< \dfrac{5}{12}\)

Giải giúp theo cách lớp 6 với ạ

Answer 1

Ta có: \(\dfrac{-4}{15}< \dfrac{5x-1}{18}< \dfrac{5}{12}\)

\(\Leftrightarrow\dfrac{-48}{180}< \dfrac{10\left(5x-1\right)}{180}< \dfrac{75}{180}\)

Suy ra: \(-48< 10\left(5x-1\right)< 75\)

\(\Leftrightarrow10\left(5x-1\right)\in\left\{-40;-30;-20;-10;0;10;20;30;40;50;60;70\right\}\)

\(\Leftrightarrow5x-1\in\left\{-4;-3;-2;-1;0;1;2;3;4;5;6;7\right\}\)

\(\Leftrightarrow5x\in\left\{-3;-2;-1;0;1;2;3;4;5;6;7;8\right\}\)

\(\Leftrightarrow x\in\left\{0;1\right\}\)(Vì x nguyên)