Đáp án:
$3.$ \(\left[ \begin{array}{l}x=4\\x=-3,2\end{array} \right.\)
$4. x = \frac{1}{10}$
$5. x = \frac{1}{66}$
$6. x = \frac{7}{36}$
Giải thích các bước giải:
$3. 3,6 - | x - 0,4 | = 0$
⇔ $| x - 0,4 | = 3,6$
⇔ \(\left[ \begin{array}{l}x-0,4=3,6\\x-0,4=-3,6\end{array} \right.\)
⇔ \(\left[ \begin{array}{l}x=4\\x=-3,2\end{array} \right.\)
$4. 2( \frac{3}{4} - 5x ) = \frac{4}{5} - 3x$
⇔ $\frac{3}{2} - 10x = \frac{4}{5} - 3x$
⇔ $10x - 3x = \frac{3}{2} - \frac{4}{5}$
⇔ $7x = \frac{15}{10} - \frac{8}{10}$
⇔ $7x = \frac{7}{10}$
⇔ $x = \frac{1}{10}$
$5. \frac{3}{2} - 4( \frac{1}{4} - x ) = \frac{2}{3} - 7x$
⇔ $\frac{3}{2} - 1 + 4x = \frac{2}{3} - 7x$
⇔ $\frac{1}{2} + 4x = \frac{2}{3} - 7x$
⇔ $4x + 7x = \frac{2}{3} - \frac{1}{2}$
⇔ $11x = \frac{4}{6} - \frac{3}{6}$
⇔ $11x = \frac{1}{6}$
⇔ $x = \frac{1}{66}$
$6. 4( \frac{1}{2} - x ) - 5( x - \frac{3}{10} ) = \frac{7}{4}$
⇔ $\frac{4}{2} - 4x - 5x + \frac{3}{2} = \frac{7}{4}$
⇔ $\frac{4}{2} + \frac{3}{2} - 9x = \frac{7}{4}$
⇔ $\frac{7}{2} - 9x = \frac{7}{4}$
⇔ $\frac{14}{4} - 9x = \frac{7}{4}$
⇔ $9x = \frac{14}{4} - \frac{7}{4}$
⇔ $9x = \frac{7}{4}$
⇔ $x = \frac{7}{36}$
