Bài 2:
a) $\frac{3}{4}+\frac{2}{3}x=\frac{1}{2}$
$\frac{2}{3}x=\frac{1}{2}-\frac{3}{4}$
$\frac{2}{3}x=\frac{2}{4}-\frac{3}{4}$
$\frac{2}{3}x=\frac{-1}{4}$
$x=\frac{-1}{4}:\frac{2}{3}$
$x=\frac{-1}{4}.\frac{3}{2}$
$x=\frac{-3}{8}$
Vậy $x=\frac{-3}{8}$
b) $|x-\frac{7}{10}|-\frac{1}{5}=0$
$|x-\frac{7}{10}|=\frac{1}{5}$
TH1: $x-\frac{7}{10}=\frac{1}{5}$
$x=\frac{1}{5}+\frac{7}{10}$
$x=\frac{2}{10}+\frac{7}{10}$
$x=\frac{9}{10}$
TH2: $x-\frac{7}{10}=\frac{-1}{5}$
$x=\frac{-1}{5}+\frac{7}{10}$
$x=\frac{-2}{10}+\frac{7}{10}$
$x=\frac{5}{10}$
$x=\frac{1}{2}$
Vậy $x=\frac{9}{10}$ hoặc $x=\frac{1}{2}$
c) $\frac{x}{-4}=\frac{-9}{x}$
$x.x=(-4).(-9)$
$x^2=36$
$x^2=6^2$ hoặc $x^2=(-6)^2$
$x=6$ hoặc $x=-6$
Vậy $x=6$ hoặc $x=-6$
