Câu 1.

$\frac{1}{15}-\frac{9}{15}=\frac{-8}{15}$

$\frac{2}{15}-\frac{10}{15}=\frac{-8}{15}$

$\frac{3}{15}-\frac{11}{15}=\frac{-8}{15}$

Câu 2:

$\frac{-9}{15}+\frac{1}{15}=\frac{-8}{15}$

$\frac{-10}{15}+\frac{2}{15}=\frac{-8}{15}$

$\frac{-11}{15}+\frac{3}{15}=\frac{-8}{15}$

Câu 3:

$\frac{-7}{15}-\frac{1}{15}=\frac{-8}{15}$

$\frac{-6}{15}-\frac{2}{15}=\frac{-8}{15}$

$\frac{-5}{15}-\frac{3}{15}=\frac{-8}{15}$

a, - \(\dfrac{11}{25}\) = \(\dfrac{-6}{25}\) + \(\dfrac{-5}{25}\) + 

    - \(\dfrac{11}{25}\) =  \(\dfrac{-1}{25}\) + \(\dfrac{-10}{25}\) + 

    - \(\dfrac{11}{25}\) = \(\dfrac{-3}{25}\) + \(\dfrac{-8}{25}\) +  

b, - \(\dfrac{11}{25}\) = \(\dfrac{6}{25}\) - \(\dfrac{17}{25}\)

   - \(\dfrac{11}{25}\) = \(\dfrac{7}{25}\) - \(\dfrac{18}{25}\)

  - \(\dfrac{11}{25}\)  = \(\dfrac{8}{25}\) - \(\dfrac{19}{25}\)

a) 3/8 = 1/8 + 2/8 = 1/8 + 1/4

3/8 = 5/8 - 2/8 = 5/8 - 1/4

b) 5/12 = 1/12 + 4/12 = 1/12 + 1/3

5/12 = 7/12 - 2/12 = 7/12 - 1/6

c) 1/11 = -2/11 + 3/11

1/11 = 2/11 - 1/11

d) 1/4 = -2/4 + 3/4 = -1/2 + 3/4

1/4 = 5/4 - 4/4 = 5/4 -1

a) \(-\dfrac{7}{13}=\dfrac{-3}{13}+\dfrac{-4}{13}\)

b) \(-\dfrac{11}{25}=\dfrac{6}{25}-\dfrac{17}{25}\)

a) Cách 1 : \(-\dfrac{7}{13}=\dfrac{-6-7}{13}=-\dfrac{6}{13}-\dfrac{7}{13}\)

Cách 2 : \(-\dfrac{7}{13}=-\dfrac{1}{13}-\dfrac{10}{13}\)

b) Cách 1 : \(-\dfrac{11}{25}=\dfrac{10}{25}-\dfrac{21}{25}\)

Cách 2 : \(-\dfrac{11}{25}=\dfrac{9}{25}-\dfrac{22}{25}\)

\(\frac{-2}{15}\) + \(\frac{2}{15}\)

\(\frac{-3}{15}\) + \(\frac{3}{15}\)

\(\frac{-4}{15}\)+ \(\frac{4}{15}\)

− 11 25 = − 1 25 + − 6 25 ; − 11 25 = − 3 25 + − 8 25 ; − 11 25 = − 2 25 + − 9 25

dưới dạng tổng của hai số hữu tỉ âm.

− 4 15 = − 1 15 + 1 5 ; − 4 15 = − 1 30 + − 7 30 ; − 4 15 = − 2 15 + 2 15