Tìm x a) 0,25x - 1/3 = -5/3 b) (2/3x + 1/2)*-5/6 = 3

* Hướng dẫn giải

a) $0,25x-\frac{1}{3}=\frac{-5}{3}$ 

$0,25x=\frac{-5}{3}+\frac{1}{3}$ 

$0,25x=\frac{(-5)+1}{3}$ 

$0,25x=\frac{-4}{3}$ 

$x=\frac{-4}{3}:0,25$ 

$x=\frac{-4}{3}:\frac{1}{4}$ 

$x=\frac{-4}{3}.\frac{4}{1}$ 

$x=\frac{-16}{3}$ 

b) $(\frac{2}{3}x+\frac{1}{2}).\frac{-5}{6}=3$ 

$\frac{2}{3}x+\frac{1}{2}=3:\left(\frac{-5}{6}\right)$ 

$\frac{2}{3}x+\frac{1}{2}=3.\left(\frac{6}{-5}\right)$ 

$\frac{2}{3}x+\frac{1}{2}=\frac{3}{1}.\frac{6}{-5}$ 

$\frac{2}{3}x+\frac{1}{2}=\frac{18}{-5}$ 

$\frac{2}{3}x=\frac{18}{-5}-\frac{1}{2}$ 

$\frac{2}{3}x=\frac{18.2}{(-5).2}-\frac{1}{2.(-5)}$ 

$\frac{2}{3}x=\frac{36}{-10}-\frac{1}{-10}$ 

$\frac{2}{3}x=\frac{35}{-10}$ 

$x=\frac{35}{-10}:\frac{2}{3}$ 

$$\begin{gathered} x=\frac{35}{-10}.\frac{3}{2} \\ x=\frac{\mathrm{5.7.3}}{5.(-2).2} \\ x=\frac{21}{-4} \end{gathered}$$