Đáp án:
Giải thích các bước giải:
a)
MSC là : 75
$\dfrac{7}{-15}$=$\dfrac{-7}{15}$=$\dfrac{35}{75}$
$\dfrac{-8}{-25}$=$\dfrac{8}{25}$=$\dfrac{24}{75}$
$\dfrac{11}{75}$=$\dfrac{-11}{75}$
b)
MSC là : 180
$\dfrac{-8}{-45}$=$\dfrac{8}{45}$=$\dfrac{32}{180}$
$\dfrac{13}{180}$=$\dfrac{-3}{180}$
$\dfrac{-4}{-30}$=$\dfrac{4}{30}$=$\dfrac{24}{180}$