a) Cách 1:

 \(\begin{array}{l}\left( {\frac{{ - 2}}{{ - 5}} + \frac{{ - 5}}{{ - 6}}} \right) + \frac{4}{5} = \frac{2}{5} + \frac{5}{6} + \frac{4}{5}\\ = \frac{{12}}{{30}} + \frac{{25}}{{30}} + \frac{{24}}{{30}} = \frac{{61}}{{30}}\end{array}\)

Cách 2:

\(\begin{array}{l}\left( {\frac{{ - 2}}{{ - 5}} + \frac{{ - 5}}{{ - 6}}} \right) + \frac{4}{5} = \left( {\frac{2}{5} + \frac{4}{5}} \right) + \frac{5}{6}\\ = \frac{6}{5} + \frac{5}{6} = \frac{{36}}{{30}} + \frac{{25}}{{30}} = \frac{{61}}{{30}}\end{array}\)

b) Cách 1:

 \(\begin{array}{l}\frac{{ - 3}}{{ - 4}} + \left( {\frac{{11}}{{ - 15}} + \frac{{ - 1}}{2}} \right) = \frac{3}{4} + \frac{{ - 11}}{{15}} + \frac{{ - 1}}{2}\\ = \frac{{45}}{{60}} + \frac{{ - 44}}{{60}} + \frac{{ - 30}}{{60}}\\ = \frac{{ - 29}}{{60}}\end{array}\).

Cách 2:

\(\begin{array}{l}\frac{{ - 3}}{{ - 4}} + \left( {\frac{{11}}{{ - 15}} + \frac{{ - 1}}{2}} \right) = \frac{3}{4} + \frac{{ - 11}}{{15}} + \frac{{ - 1}}{2}\\ = \left( {\frac{3}{4} + \frac{{ - 1}}{2}} \right) + \frac{{ - 11}}{{15}}\\ = \left( {\frac{3}{4} + \frac{{ - 2}}{4}} \right) + \frac{{ - 11}}{{15}}\\ = \frac{1}{4} + \frac{{ - 11}}{{15}}\\ = \frac{{15}}{{60}} + \frac{{ - 44}}{{60}}\\ = \frac{{ - 29}}{{60}}\end{array}\)

a)

 \(\begin{array}{l}M = \frac{1}{7}.(\frac{{ - 5}}{8}) + \frac{1}{7}.(\frac{{ - 11}}{8})\\ = \frac{{ - 5}}{{56}} + \frac{{ - 11}}{{56}} = \frac{{ - 16}}{{56}} = \frac{{ - 2}}{7}\end{array}\)

b)

\(\begin{array}{l}M = \frac{1}{7}.(\frac{{ - 5}}{8}) + \frac{1}{7}.(\frac{{ - 11}}{8})\\ = \frac{1}{7}.[(\frac{{ - 5}}{8}) + (\frac{{ - 11}}{8})]\\ = \frac{1}{7}.\frac{{ - 16}}{8}\\ = \frac{1}{7}.( - 2)\\ = \frac{{ - 2}}{7}\end{array}\)

C₁: dễ nên tự làm nhé

C₂: \(A=\left(6-\frac{2}{3}+\frac{1}{2}\right)-\left(5+\frac{5}{3}-\frac{3}{2}\right)-\left(3-\frac{7}{2}+\frac{5}{2}\right)\)

\(=6-\frac{2}{3}+\frac{1}{2}-5-\frac{5}{3}+\frac{3}{2}-3+\frac{7}{3}-\frac{5}{2}\)

\(=6-5-3+\left(\frac{1}{2}+\frac{3}{2}-\frac{5}{2}\right)-\left(\frac{2}{3}+\frac{5}{3}-\frac{7}{3}\right)\)

\(=-2-\frac{1}{2}=\frac{-4}{2}-\frac{1}{2}=\frac{-5}{2}\)

a) c1 := -2/-5+-5/-6+4/5

=2/5+5/6+4/5

=12/30+25/30+24/30

=61/30

c2:=(2/5+4/5)+4/5

=(2/5+4/5)+5/6

=6/5+5/6

=36/30+25/30

=61/30

b)c1:=-3/-4+11/-15+-1/2

=3/4+-11/15+-1/2

=45/60+-44/30+-30/60

-29/30

c2:=3/4+(-11/15+-1/2)

=(3/4+-1/2)+-11/15

=(3/4+-2/4)+-11/5

=1/4+-11/15

=15/60+-44/60

=-29/60

\(\begin{array}{l}B = \left( {\frac{{ - 3}}{{13}}} \right) + \frac{{16}}{{23}} + \left( {\frac{{ - 10}}{{13}}} \right) + \frac{5}{{11}} + \frac{7}{{23}}\\ = \left[ {\left( {\frac{{ - 3}}{{13}}} \right) + \left( {\frac{{ - 10}}{{13}}} \right)} \right] + \left[ {\frac{{16}}{{23}} + \frac{7}{{23}}} \right] + \frac{5}{{11}}\\ =  - 1 + 1 + \frac{5}{{11}}\\ = \frac{5}{{11}}\end{array}\)

`B= ( (-3)/13 + (-10)/13) + (16/23 + 7/23 ) +5/11`

`B= -13/13 + 23/23 +5/11`

`B=-1+1+5/11`

`B=0+5/11`

`B=5/11`

\(B=\left(-\dfrac{3}{13}\right)+\dfrac{16}{23}+\left(-\dfrac{10}{13}\right)+\dfrac{5}{11}+\dfrac{7}{23}\)

\(B=\left[\left(-\dfrac{3}{13}\right)+\left(-\dfrac{10}{13}\right)\right]+\left(\dfrac{16}{23}+\dfrac{7}{23}\right)+\dfrac{5}{11}\)

\(B=\left(-1\right)+1+\dfrac{5}{11}\)

\(B=\dfrac{5}{11}\)

Cách 1:

A = \(\left(6-\frac{2}{3}+\frac{1}{2}\right)-\left(5+\frac{5}{3}-\frac{3}{2}\right)-\left(3-\frac{7}{3}+\frac{5}{2}\right)\)

A = \(\frac{35}{6}-\frac{31}{6}-\frac{19}{6}\)

A = \(\frac{-15}{6}=\frac{-5}{2}\)

Cách 2:

A = \(\left(6-\frac{2}{3}+\frac{1}{2}\right)-\left(5+\frac{5}{3}-\frac{3}{2}\right)-\left(3-\frac{7}{3}+\frac{5}{2}\right)\)

A = \(6-\frac{2}{3}+\frac{1}{2}-5-\frac{5}{3}+\frac{3}{2}-3+\frac{7}{3}-\frac{5}{2}\)

A = \(6-5-3-\frac{2}{3}-\frac{5}{3}+\frac{7}{3}+\frac{1}{2}+\frac{3}{2}-\frac{5}{2}\)

A = \(\left(6-5-3\right)-\left(\frac{2}{3}+\frac{5}{3}-\frac{7}{3}\right)+\left(\frac{1}{2}-\frac{3}{2}-\frac{5}{2}\right)\)

A = \(-2-0+\left(2-\frac{5}{2}\right)\)

A = \(-2+\left(2-\frac{5}{2}\right)\)

A = \(-2+2-\frac{5}{2}\)

A = \(0-\frac{5}{2}\)

A = \(\frac{-5}{2}\)

Cách 1:A=(6−2/3+1/2)−(5+5/3−3/2)−(3−7/3+5/2)

               = ( 36/6  - 4/6 + 3/6)-(30/6 + 10/6 - 9/6) -(18/6 -14/6 +15/6)

               =             35/6         -               31/6         -          19/6

                =          -15/2

Cách 2: A=(6−2/3+1/2)−(5+5/3−3/2)−(3−7/3+5/2)

                = 6- 2/3 +1/2 - 5 - 5/3 + 3/2 - 3 + 7/3 -5/2

                = (6-5-3) + ( -2/3-5/3+7/3) + (1/2+3/2-5/2)

                =    -2      +           0            -          1/2

                = -2 - 1/2 = -4/2 - 1/2 = -5/2

\(A=\left(6-\frac{2}{3}+\frac{1}{2}\right)-\left(5+\frac{5}{3}-\frac{3}{2}\right)-\left(3-\frac{7}{3}+\frac{5}{2}\right)\)

\(A=6-\frac{2}{3}+\frac{1}{2}-5-\frac{5}{3}+\frac{3}{2}-3+\frac{7}{3}-\frac{5}{2}\)

\(A=\left(6-5-3\right)-\left(\frac{2}{3}+\frac{5}{3}-\frac{7}{3}\right)+\left(\frac{1}{2}+\frac{3}{2}-\frac{5}{2}\right)\)

\(A=-2+\frac{-1}{2}\)

\(A=-\frac{5}{2}\)

Vậy A= -5/2

Mình không đọc kĩ, sorry bạn nhiều 

A = (6 - 2/3 + 1/2) - (5 + 5/3 - 3/2) - (3 - 7/3 + 5/2)

A= ( 36/6 - 4/6 + 3/6) -( 30/6 + 10/6 - 9/6) - ( 18/6 - 14/6 + 15/6)

A= 35/6 - 31/6 -19/6

A= -5/2

Vậy A= - 5/2

Cách 2 đâu bn

ủng hộ mk nha mọi người