Câu 8:
a: \(\dfrac{-45}{-125}=\dfrac{45}{125}=\dfrac{45:5}{125:5}=\dfrac{9}{25}\)
b: \(\dfrac{-300}{200}=\dfrac{-300:100}{200:100}=\dfrac{-3}{2}\)
c: \(\dfrac{63}{-7}=\dfrac{-63}{7}=\dfrac{-63:7}{7:7}=\dfrac{-9}{1}=-9\)
Câu 9:
\(4=\dfrac{4\cdot8}{8}=\dfrac{32}{8}\)
\(-7=\dfrac{-7\cdot8}{8}=\dfrac{-56}{8}\)
\(13=\dfrac{13\cdot8}{8}=\dfrac{104}{8}\)
Câu 10:
\(3=\dfrac{3\cdot\left(-7\right)}{-7}=\dfrac{-21}{-7}\)
\(-5=\dfrac{\left(-5\right)\cdot\left(-7\right)}{-7}=\dfrac{35}{-7}\)
\(13=\dfrac{13\cdot\left(-7\right)}{-7}=\dfrac{-91}{-7}\)
Câu 11:
\(\dfrac{-9}{39}=\dfrac{-3}{13};\dfrac{12}{9}=\dfrac{4}{3};\dfrac{35}{10}=\dfrac{7}{2}\)
