Question

Tính nhanh:

\(B=\dfrac{-5}{9}+\dfrac{8}{15}+\dfrac{-2}{11}+\dfrac{4}{-9}+\dfrac{7}{15}\)

Answer 1

B=-5/9+8/15+-2/11+4/9+7/15

=>B=(-5/9+4/-9)+(8/15+7/15)-2/11

=>B=(-5/9+-4/9)+1-2/11

=>B=-1+1-2/11

=>B=-2/11

Vậy B=-2/11

Answer 2

Ta có :

B=-5/9+8/15+-2/11+4/9+7/15

=>B=(-5/9+4/-9)+(8/15+7/15)-2/11

=>B=(-5/9+-4/9)+1-2/11

=>B=-1+1-2/11

=>B=-2/11

Vậy B=-2/11

Answer 3

,−59+815+−211+4−9+715-59+815+-211+4-9+715

 

=(−59+4−9)+(815+715)−211=(-59+4-9)+(815+715)-211

 

=−1+1−211=-1+1-211

 

=−211

Answer 4

Ta có: \(B=\dfrac{-5}{9}+\dfrac{8}{15}+\dfrac{-2}{11}+\dfrac{4}{-9}+\dfrac{7}{15}\)

\(=\left(\dfrac{-5}{9}+\dfrac{-4}{9}\right)+\left(\dfrac{8}{15}+\dfrac{7}{15}\right)+\dfrac{-2}{11}\)

\(=-1+1+\dfrac{-2}{11}\)

\(=-\dfrac{2}{11}\)

Answer 5

Theo đề,ta có 

B=-5/9+8/15+-2/11+4/9+7/15

=>B=(-5/9+4/-9)+(8/15+7/15)-2/11

=>B=(-5/9+-4/9)+1-2/11

=>B=-1+1-2/11

=>B=-2/11

Vậy B=-2/11

Answer 6

\(B=\dfrac{-5}{9}+\dfrac{8}{15}+\dfrac{-2}{11}+\dfrac{4}{-9}+\dfrac{7}{15}\)

\(\text{​​}\text{​​}\text{​​}B=\dfrac{-5}{9}+\dfrac{8}{15}+\dfrac{-2}{11}+\dfrac{-4}{9}+\dfrac{7}{15}\)

\(B=(\dfrac{-5}{9}+\dfrac{-4}{9})+(\dfrac{8}{15}+\dfrac{7}{15})+\dfrac{-2}{11}\)

\(B=\dfrac{-9}{9}+\dfrac{15}{15}+\dfrac{-2}{11}\)

\(B=-1+1+\dfrac{-2}{11}\)

\(B=0+\dfrac{-2}{11}\)

\(B=\dfrac{-2}{11}\)

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Answer 7

B=-5/9+8/15+-2/11+4/9+7/15

=>B=(-5/9+4/-9)+(8/15+7/15)-2/11

=>B=(-5/9+-4/9)+1-2/11

=>B=-1+1-2/11

=>B=-2/11

Vậy B=-2/11