Đáp án:
`3x - 75% x = -1,2`
` 3x - 3/4 x = -1,2`
` x(3 - 3/4) = -1,2`
` 9/4 x = -1,2`
` x = -6/5 : 9/4`
` x = -8/15`
`|2/3x - 1/4| - 1 = 0,5`
`|2/3x - 1/4| = 0,5 + 1`
`|2/3x - 1/4| = 3/2`
⇒\(\left[ \begin{array}{l}\frac{2}{3}x - \frac{1}{4} = \frac{3}{2}\\\frac{2}{3}x - \frac{1}{4} = -\frac{3}{2}\end{array} \right.\)
⇒\(\left[ \begin{array}{l}\frac{2}{3}x = \frac{7}{4}\\\frac{2}{3}x = -\frac{5}{4}\end{array} \right.\)
⇒\(\left[ \begin{array}{l}x = \frac{21}{8}\\x = -\frac{15}{8}\end{array} \right.\)
Vậy `x \in {21/8 ; -15/8}`
