Bài 1:
$\frac{2}{-5}=$ $\frac{-4}{10}$
$\frac{-3}{4}=$ $\frac{-6}{8}$
$\frac{1}{-9}=$ $\frac{-2}{18}$
$\frac{-4}{-13}=$ $\frac{8}{26}$
$\frac{0}{-7}=0$
Bài 2:
a, $\frac{3}{-5}=$ $\frac{-6}{10}=$ $\frac{-9}{15}$
b, $\frac{5}{-10}=$ $\frac{-10}{20}=$ $\frac{-15}{30}$
c, $\frac{-6}{-8}=$ $\frac{6}{8}=$ $\frac{12}{16}$
d, $\frac{0}{-10}=0=$ $\frac{0}{26}=$ $\frac{0}{73}$