$B1:$ A
$B2:$ $\dfrac{9}{-7}=\dfrac{-9}{7}$
$\dfrac{-4}{-3}=\dfrac{4}{3}$
$\dfrac{-6}{-11}=\dfrac{6}{11}$
$\dfrac{2}{-13}=\dfrac{-2}{13}$
$B3:$
$a)$
$\dfrac{3}{2}=\dfrac{12}{8}$
$\dfrac{2}{3}=\dfrac{8}{12}$
$\dfrac{2}{8}=\dfrac{3}{12}$
$\dfrac{8}{2}=\dfrac{12}{3}$
$b)$ Tương tự
$B4:$ Tương tự
$B5:$
$a) \dfrac{1}{6}=\dfrac{x}{18}$
$\to 6x=18$
$\to x=3$
$b)$ $\dfrac{x}{8}=\dfrac{-1}{4}$
$\to 4x=-8$
$\to x=-2$
$c)$ $\dfrac{4}{-5}=\dfrac{x}{10}$
$\to 40=-5x$
$\to x=-8$
$d)$ $\dfrac{11}{5}=\dfrac{-22}{x}$
$\to -110=11x$
$\to x=-10$
$e)$ $\dfrac{x}{8}=\dfrac{8}{x}$
$\to x^2=64$
$\to x= 8$ hoặc $x=-8$
$f)$ $\dfrac{x}{-11}=\dfrac{-11}{x}$
$\to x^2=121$
$\to x=11$ hoặc $x=-11$
