Tìm x, biết: a) (0,5x-3/7):1/2=1 1/7 b) |2 − 3x| − 5 = −1 c) (1/5-3/2)^2=9/4 .

a) $(\mathrm{0,5}x-\frac{3}{7}):\frac{1}{2}=1\frac{1}{7}$

$\mathrm{0,5}x-\frac{3}{7}=1\frac{1}{7}.\frac{1}{2}$

$\mathrm{0,5}x-\frac{3}{7}=\frac{8}{7}.\frac{1}{2}$

$\mathrm{0,5}x-\frac{3}{7}=\frac{4}{7}$

$\mathrm{0,5}x=\frac{4}{7}+\frac{3}{7}$

0,5x = 1

x = 1 : 0,5

x = 2.

Vậy x = 2.

b) |2 − 3x| − 5 = −1

|2 − 3x| = 5 −1

|2 − 3x| = 4

Trường hợp 1: 2 − 3x = 4

3x = 2 − 4

3x = −2

$x=\frac{-2}{3}$.

Trường hợp 2: 2 − 3x = −4

3x = 2 + 4

3x = 6

x = 2.

Vậy $x\in \{\frac{-2}{3};2\}$.

c) ${(\frac{1}{5}-\frac{3}{2}x)}^2=\frac{9}{4}{(\frac{1}{5}-\frac{3}{2}x)}^2=\frac{9}{4}$

Trường hợp 1: $\frac{3}{2}x=\frac{1}{5}-\frac{3}{2}$

$\frac{3}{2}x=\frac{2}{10}-\frac{15}{10}$

$\frac{3}{2}x=\frac{2}{10}-\frac{15}{10}$

$\frac{3}{2}x=\frac{-13}{10}$

$x=\frac{-13}{10}:\frac{3}{2}$

$x=\frac{-13}{15}$.

Trường hợp 2: $\frac{1}{5}-\frac{3}{2}x=-\frac{3}{2}$

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

$\frac{3}{2}x=\frac{17}{10}$

$x=\frac{17}{10}:\frac{3}{2}$

$x=\frac{17}{15}$.

Vậy $x\in \{\frac{-13}{15};\frac{17}{15}\}$.