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) \(\dfrac{-7}{20}=\dfrac{1}{5}.\dfrac{-7}{4}\) b) \(\dfrac{-7}{20}=\dfrac{-7}{40}:\dfrac{1}{2}\) c) \(\dfrac{-7}{20}=\dfrac{2}{5}+\dfrac{-3}{4}\) d) \(\dfrac{-7}{20}=\dfrac{-1}{5}+\dfrac{-3}{20}\)

a)\(\dfrac{-7}{20}=\dfrac{-7}{10}\times\dfrac{1}{2}\)

b)\(\dfrac{-7}{20}=\dfrac{-7}{40}\times\dfrac{1}{2}\)

c)\(\dfrac{-7}{20}=\dfrac{7}{20}+\dfrac{-7}{10}\)

d)\(\dfrac{-7}{20}=\dfrac{-1}{5}+\dfrac{-3}{20}\)

\(\frac{-2}{15}\) + \(\frac{2}{15}\)

\(\frac{-3}{15}\) + \(\frac{3}{15}\)

\(\frac{-4}{15}\)+ \(\frac{4}{15}\)

A)\(-\frac{7}{20}=\frac{1}{10}.\left(-\frac{7}{2}\right)\)

B)  

a) \(-\frac{15}{32}=-\frac{1}{4}+\left(-\frac{7}{32}\right)\)

b) \(-\frac{15}{32}=\frac{1}{32}-\frac{1}{2}\)

-11/15 = -6/15 + (-5/15) = -2/5 + (-1/3)

-11/15 = -1/15 + (-10/15) = -1/15 + (-2/3)

-11/15 = -4/15 + (-7/15)

Nguyễn Minh bạn chỉ đăng 1,2 câu trả lời thôi nhé , chứ dài quá

Mình sẽ làm bài 1,2

1.\(a,\frac{61}{11}x+\frac{97}{11}x+\frac{25}{11}=\frac{37}{11}x-\frac{8}{11}\)

\(\Leftrightarrow\frac{61}{11}x+\frac{97}{11}x+\frac{25}{11}-\frac{37}{11}x=-\frac{8}{11}\)

\(\Leftrightarrow\frac{61}{11}x+\frac{97}{11}x-\frac{37}{11}x+\frac{25}{11}=-\frac{8}{11}\)

\(\Leftrightarrow\frac{121}{11}x=-3\)

\(\Leftrightarrow11x=-3\Leftrightarrow x=-\frac{3}{11}\)

\(b,3x-\frac{15}{5\cdot8}-\frac{15}{8\cdot11}-\frac{15}{11\cdot14}-...-\frac{15}{47\cdot50}=\frac{21}{10}\)

\(3x-\left[\frac{15}{5\cdot8}-\frac{15}{8\cdot11}-\frac{15}{11\cdot14}-...-\frac{15}{47\cdot50}\right]=\frac{21}{10}\)

\(3x-\left[5\left\{\frac{3}{5\cdot8}-\frac{3}{8\cdot11}-\frac{3}{11\cdot14}-...-\frac{3}{47\cdot50}\right\}\right]=\frac{21}{10}\)

Làm nốt :v

2. Gọi hai phân số đó là \(\frac{a}{b}\)và \(\frac{c}{d}\)

Theo đề bài ta có : \(\frac{a}{b}+\frac{c}{d}=\frac{4}{33}\Rightarrow\frac{ad+bc}{bd}=\frac{4}{33}\Rightarrow ad+bc=\frac{4}{33}bd\)

\(\frac{a}{b}\cdot\frac{c}{d}=-\frac{4}{11}\Rightarrow\frac{bd}{ac}=\frac{-11}{4}\)

Tổng các số nghịch đảo của hai phân số trên là :

\(\frac{b}{a}+\frac{d}{c}=\frac{bc+ad}{ac}=\frac{\frac{4}{33}bd}{ac}=\frac{4}{33}\cdot\left[-\frac{11}{4}\right]=-\frac{1}{3}\)