\(-\dfrac{3}{17}+\left(\dfrac{2}{3}+\dfrac{3}{17}\right)=\dfrac{-3}{17}+\dfrac{3}{17}+\dfrac{2}{3}=\dfrac{2}{3}\)

\(\dfrac{-5}{21}+\dfrac{-16}{21}+1=-1+1=0\)

\(\dfrac{-4}{11}\cdot\dfrac{5}{15}\cdot\dfrac{11}{-4}=\dfrac{5}{15}=\dfrac{1}{3}\)

a: =-5/11-6/11+1=-11/11+1=0

b: =-13/17-13/21-4/17=-1-13/21=-34/21

b: \(=-\dfrac{5}{12}\cdot\dfrac{9}{20}\cdot\dfrac{7}{17}=\dfrac{-21}{272}\)

d: \(=\dfrac{13}{17}\left(-\dfrac{4}{5}-\dfrac{3}{4}\right)=\dfrac{13}{17}\cdot\dfrac{-31}{20}=\dfrac{-403}{340}\)

`a// [-3]/5+7/21+[-4]/5+7/5=([-3]/5+[-4]/5+7/5)+7/21=0/5+7/21=7/21`

`b// [-3]/17+(2/3+3/17)=[-3]/17+2/3+3/17=([-3]/17+3/17)+2/3=0/17+2/3=2/3`

`c// [-5]/21+([-16]/21+1)=[-5]/21+[-16]/21+1=([-5]/21+[-16]/21)+1=[-21]/21+1=-1+1=0`

a) \(\dfrac{-3}{5}+\dfrac{7}{21}+\dfrac{-4}{5}+\dfrac{7}{5}\)

\(=\left(-\dfrac{3}{5}+\dfrac{-4}{5}+\dfrac{7}{5}\right)+\dfrac{7}{21}\)

\(=0+\dfrac{7}{21}\)

\(=\dfrac{7}{21}\)

b) `-3/17 + ( 2/3 + 3/17)`

` = -3/17 +  2/3 + 3/17`

` = 2/3 + ( -3/17 +3/17)`

` = 2/3 + 0`

` = 2/3`

c) 

` -5/21 + ( -16/21 +1)`

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

\(=\left(\dfrac{-5}{21}+\dfrac{-16}{21}\right)+1\)

\(=-1+1=0\)

6/21; 7/21; 8/21; 9/21; 10/21; 11/21; 12/21; 13/21; 14/21; 15/21; 16/21

Bạn cần làm gì với những phân số này?

Đề là j em nhỉ ?

tính

6/21; 7/21; 8/21; 9/21; 10/21; 11/21; 12/21; 13/21; 14/21; 15/21; 16/21

\(\dfrac{1}{21}+\dfrac{2}{21}+\dfrac{3}{21}+\dfrac{4}{21}+\dfrac{5}{21}+...+\dfrac{17}{21}+\dfrac{18}{21}+\dfrac{19}{21}+\dfrac{20}{21}\)

\(=\dfrac{1+2+3+4+5+...+17+18+19+20}{21}\)

\(=\dfrac{1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20}{21}\)

\(=\dfrac{210}{21}\)

\(=10\)

ai làm giúp mình vs ạ mình đang cần gấp

\(5:\dfrac{2}{3}\)\(=5\times\dfrac{3}{2}=\dfrac{5\times3}{2}=\dfrac{15}{2}\)

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\(\dfrac{4}{7}+\dfrac{2}{5}=\dfrac{20}{35}+\dfrac{14}{35}=\dfrac{34}{35}\)

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\(1-\dfrac{17}{21}=\dfrac{21}{21}-\dfrac{17}{21}=\dfrac{4}{21}\)

Chúc bạn học tốt:>

`(-3)/5+7/21+(-4)/5+7/5`

`=(-3)/5+(-4)/5+7/5+7/21`

`=0+7/21=7/21`

`(-3)/17+(2/3+3/17)`

`=(-3)/17+3/17+2/3`

`=0+2/3=2/3`

\(-\dfrac{3}{5}+\dfrac{7}{21}+-\dfrac{4}{5}+\dfrac{7}{5}\)

\(=\left(\dfrac{-3-4+7}{5}\right)+\dfrac{7}{21}=0+\dfrac{7}{21}=\dfrac{7}{21}\)

\(-\dfrac{3}{17}+\left(\dfrac{2}{3}+\dfrac{3}{17}\right)=\left(-\dfrac{3}{17}+\dfrac{3}{17}\right)+\dfrac{2}{3}=0+\dfrac{2}{3}=\dfrac{2}{3}\)

\(\frac{17}{21}\times\frac{2}{5}+\frac{17}{21}\times\frac{17}{21}\times\frac{3}{5}\)

\(=\frac{17}{21}\times\left(\frac{2}{5}+\frac{3}{5}\right)\)

\(=\frac{17}{21}\times1\)

\(=\frac{17}{21}\)

Đề bài hơi kì. Bạn kiểm tra lại xem có sai chỗ nào ko v?