= 5/2

1, \(\frac{5}{21}+0,5-\frac{19}{23}+\frac{16}{21}-\frac{4}{23}\)

\(=\frac{5+16}{21}-\frac{19+4}{23}+0,5\)

\(=1-1+0,5\)

\(=0,5\)

2,\(\frac{27}{23}+\frac{5}{21}-\frac{4}{23}+\frac{6}{21}+\frac{1}{2}\)

\(=\frac{27-4}{23}+\frac{5+6}{21}+\frac{1}{2}\)

\(=1+\frac{11}{21}+\frac{1}{2}\)

\(=\frac{42+22+21}{42}\)

\(=\frac{85}{42}\)

\(\Rightarrow A=\left(\frac{27}{23}-\frac{4}{23}\right)+\left(\frac{5}{21}+\frac{16}{21}\right)+\frac{1}{2}\)

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

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

tíc mình nha

A=1+1+1/2

A=5/2

=5/2 nhé

Bài 1:

a, Ta có: \(\dfrac{27}{23}+\dfrac{5}{21}-\dfrac{4}{23}+\dfrac{16}{21}+\dfrac{1}{2}\)

= \(\left(\dfrac{27}{23}-\dfrac{4}{23}\right)+\left(\dfrac{5}{21}+\dfrac{16}{21}\right)+\dfrac{1}{2}\)

=\(\dfrac{23}{23}+\dfrac{21}{21}+\dfrac{1}{2}\) = \(1+1+\dfrac{1}{2}\)

= \(2\dfrac{1}{2}\)

b: \(=\dfrac{3}{2}-\dfrac{5}{6}:\dfrac{1}{4}+2=\dfrac{7}{2}-\dfrac{5}{6}\cdot4=\dfrac{7}{2}-\dfrac{10}{3}\)

\(=\dfrac{21-20}{6}=\dfrac{1}{6}\)

a: \(=\left(\dfrac{27}{23}-\dfrac{4}{23}\right)+\left(\dfrac{5}{21}+\dfrac{16}{21}\right)+\dfrac{1}{2}=2+\dfrac{1}{2}=\dfrac{5}{2}\)

27/23 + 5/21 - 4/23 + 0,5 + 16/21

= (27/23 - 4/23) + (5/12 + 16/21) + 0,5

= 1 + 1 + 0,5

= 2,5

27/23 + 5/21 - 4/23 + 0,5 + 16/21

= (27/23 - 4/23) + (5/12 + 16/21) + 0,5

= 1 + 1 + 0,5

= 2,5

Chúc bn học tốt!!!

1: Ta có: \(2155-\left(174+2155\right)+\left(-68+174\right)\)

\(=2155-174-2155-68+174\)

=-68

2) Ta có: \(-25\cdot72+25\cdot21-49\cdot25\)

\(=-25\cdot\left(72-21+49\right)\)

\(=-25\cdot100=-2500\)

\(1\dfrac{4}{23}+\left(\dfrac{5}{21}-\dfrac{4}{23}\right)+\dfrac{16}{21}-\dfrac{1}{2}\)

\(=1\dfrac{4}{23}-\dfrac{4}{23}+\dfrac{5}{21}+\dfrac{16}{21}+\dfrac{1}{2}\)

\(=1+1-\dfrac{1}{2}\)

\(=\dfrac{3}{2}\)

1 4/23 + ( 5/21-4/23 ) + 16/21 - 1/2
=1 4/23 - 4/23 + 5/21 + 16/21 + 1/2
= 1+1-1/2
=3/2

\(\text{∘ Ans}\)

`A =`\(\left(\dfrac{27}{23}+\dfrac{1}{2}\right)-\left(\dfrac{5}{21}+\dfrac{4}{23}\right)-\dfrac{37}{21}\)

`=`\(\dfrac{27}{23}+\dfrac{1}{2}-\dfrac{5}{21}-\dfrac{4}{23}-\dfrac{37}{21}\)

`=`\(\left(\dfrac{27}{23}-\dfrac{4}{23}\right)+\left(-\dfrac{5}{21}-\dfrac{37}{21}\right)+\dfrac{1}{2}\)

`=`\(\dfrac{23}{23}-\dfrac{42}{21}+\dfrac{1}{2}=1-2+0,5=1-1,5=-0,5\)

-0,5

\(a,\dfrac{3}{5}+\dfrac{-5}{9}=\dfrac{27-25}{45}=\dfrac{2}{49}.\)

\(c,\dfrac{-27}{23}+\dfrac{5}{21}+\dfrac{4}{23}+\dfrac{16}{21}+\dfrac{1}{2}=\dfrac{-23}{23}+\dfrac{21}{21}+\dfrac{1}{2}=-1+1+\dfrac{1}{2}=\dfrac{1}{2}.\)

\(d,\dfrac{-8}{9}+\dfrac{1}{9}.\dfrac{2}{9}+\dfrac{1}{9}.\dfrac{7}{9}=\dfrac{-8}{9}+\dfrac{1}{9}.\left(\dfrac{2}{9}+\dfrac{7}{9}\right)=\dfrac{-8}{9}+\dfrac{1}{9}.1=\dfrac{-8+1}{9}=\dfrac{-7}{9}.\)