Đáp án:
$ a) x + \dfrac{1}{4} = \dfrac{4}{3}$
$ ⇔ x = \dfrac{4}{3} - \dfrac{1}{4}$
$⇔x = \dfrac{13}{12}$
$\text{Vậy x =$\dfrac{13}{12}$}$
$b) \dfrac{3}{4} + \dfrac{2}{5}x = \dfrac{29}{60}$
$⇔ \dfrac{2}{5}x = \dfrac{29}{60} - \dfrac{3}{4}$
$⇔ \dfrac{2}{5}x = -\dfrac{4}{15}$
$⇔x= -\dfrac{4}{15} : \dfrac{2}{5}$
$⇔x = -\dfrac{2}{3}$
$\text{Vậy x= -$\dfrac{2}{3}$}$
$c) -\dfrac{12}{13}x - 5= 6\dfrac{1}{13}$
$⇔ -\dfrac{12}{13}x = \dfrac{79}{13} + 5$
$⇔ -\dfrac{12}{13}x = \dfrac{144}{13}$
$⇔x = \dfrac{144}{13} : (-\dfrac{12}{13})$
$⇔x= -12$
$\text{Vậy x = -12}$
$d)\dfrac{x}{16} = \dfrac{12}{5}$
$⇔x = \dfrac{16.12}{5}$
$⇔x = 24$
$\text{Vậy x = 24}$
$e) \dfrac{11}{12} - \dfrac{2}{5} + x= \dfrac{2}{3}$
$⇔ \dfrac{31}{60} + x = \dfrac{2}{3}$
$⇔ x = \dfrac{2}{3} - \dfrac{31}{60}$
$⇔x= \dfrac{3}{20}$
$\text{Vậy x =$\dfrac{3}{20}$}$
$g) 2x (-\dfrac{1}{7}) = 0$
$⇔ 2x = \dfrac{1}{7}$
$⇔ x = \dfrac{1}{7} : 2$
$x = \dfrac{1}{14}$
$\text{Vậy x = $\dfrac{1}{14}$}$
$h) |x | - 2,2 = 1,3$
$⇔ | x | = 1,3 + 2,2$
$⇔|x| = 3,5$
$⇔x = ±3,5$
$\text{Vậy x = ±3,5}$
$i) |x+5| - 6 = 9$
$⇔ |x +5| = 9 +6$
$⇔|x+5| = 15$
TH1 :$ x +5 =15$
$⇔ x =15-5$
$⇔x = 10$
Th2:$ x +5 = -15$
$⇔ x = -15 -5$
$⇔x = -20$
$\text{Vậy x ∈{-20 ; 10 }}$
$m) | x + \dfrac{3}{4} | - \dfrac{1}{3} = 6$
$⇔ | x+\dfrac{3}{4} | = 6 + \dfrac{1}{3}$
$⇔ | x + \dfrac{3}{4} | = \dfrac{19}{3}$
Th1: $x + \dfrac{3}{4} = \dfrac{19}{3}$
$⇔ x = \dfrac{19}{3} - \dfrac{3}{4}$
$⇔x = \dfrac{67}{12}$
Th2 : $x + \dfrac{3}{4} = -\dfrac{19}{3}$
$⇔ x = -\dfrac{19}{3} - \dfrac{3}{4}$
$⇔x= -\dfrac{85}{12}$
$\text{Vậy x ∈ { -$\dfrac{85}{12}$ ; $\dfrac{67}{12}$}}$
$n) | x - \dfrac{2}{5} | + \dfrac{3}{4} = \dfrac{11}{4}$
$⇔ | x - \dfrac{2}{5} | = \dfrac{11}{4} - \dfrac{3}{4}$
$⇔ | x - \dfrac{2}{5} | = 2$
Th1 : $ x- \dfrac{2}{5} = 2$
$⇔ x= 2 + \dfrac{2}{5}$
$⇔x= \dfrac{12}{5}$
Th2 : $x - \dfrac{2}{5} = -2$
$⇔ x = -2 + \dfrac{2}{5}$
$⇔x = -\dfrac{8}{5}$
$\text{Vậy x ∈ { -$\dfrac{8}{5}$ ; $\dfrac{12}{5}$ }}$
