Tìm x: a) x/8 = -1/4 b) 6 / x-3 = 9 / 2x-7 c) (x -1/2)^2 = 4

* Hướng dẫn giải

a) 

$\begin{array}{l}\frac{x}{8}=\frac{-1}{4}\\ x.4=-1.8\\ x.4=-8\\ x=-2\end{array}$

b)

$\begin{array}{l}\frac{6}{x-3}=\frac{9}{2x-7}\\ 6.\left(2x-7\right)=9.\left(x-3\right)\\ 12x-42=9x-27\\ 3x=15\\ x=5\end{array}$

c)

$\begin{array}{l}{\left(x-\frac{1}{2}\right)}^2=4\\ x-\frac{1}{2}=\pm 2\end{array}$

TH1:

$\begin{array}{l}x-\frac{1}{2}=2\\ x=\frac{5}{2}\end{array}$

TH2:

$\begin{array}{l}x-\frac{1}{2}=-2\\ x=-\frac{3}{2}\end{array}$

 Vậy $x=\frac{5}{2}$ hoặc $x=-\frac{3}{2}$