Tìm x thuộc Z biết: a. x -5/9 = 4/9 b. 2x -7 = -6/15 : 2/5

* Hướng dẫn giải

a. Ta có

$$\begin{gathered} x-\frac{5}{9}=\frac{4}{9} \\ x=\frac{4}{9}+\frac{5}{9} \\ x=\frac{9}{9} \\ x=1 \end{gathered}$$

b. Ta có

$$\begin{gathered} 2x-7=-\frac{6}{15}:\frac{2}{5} \\ 2x=-\frac{6}{15}.\frac{5}{2}+7 \\ 2x=-1+7=6 \\ x=3 \end{gathered}$$

c. Ta có

$$\begin{gathered} \frac{-11}{12}+\frac{5}{6}\le \frac{x}{36}\le \frac{7}{9}-\frac{3}{4} \\ \frac{-33+30}{36}\le \frac{x}{36}\le \frac{28-27}{36} \\ \frac{-3}{36}\le \frac{x}{36}\le \frac{1}{36} \\ x\in \left\{-3;-2;-1;0;1\right\} \end{gathered}$$